I have been following your (yuttadhammo) videos for some time. I had a question that I wanted to ask to someone who is experienced and familiar with meditation and Buddhism. I went to a 60 day meditation retreat in Myanmar last year. I had a great experience there and so as a result I am planning to go back again for 4 months at the end of this year. I have had some experiences during my last trip which puzzled and scared me a bit. I was disturbed on a couple of occasions by beings from other world at night. These were scary experiences that scared me to the core during the retreat. It was difficult for me to meditate and to fall asleep at night as my mind would always stay in that defense mode where it wouldn't relax and fall asleep. I talked to the teachers about it and they said to practice metta meditation and to ask these beings to not disturb my meditation. They also asked me to not be afraid and simply watch the fear. It did that and it did work for the time being but the fear overpowered me during the entire retreat although I am glad that I was able to make some good progress. I want to be better prepared this time around when I am going back again. My question is what can I do better this time so I can be well prepared and so the fear of being disturbed again does not overwhelms me? I would like to practice meditation this time by leaving fear behind. Thank you for reading this.
Maybe it would be good to change the title into "How to deal with spirits while on Vipassana-Retreat?".
Generally see them as a gift, those "teachers" appearing as spirits, for they are presenting the task that you need to fullfill to step forward.
Such disturbance is something very common and often reported by elders. It's recognised mostly as "prove" of the meditator if he is serious in goodwill, viture and objectives.
No access to vipassana for one not honest in his aspirations, for one with wrong views and lack of metta (right resolve), a person not feeling obligated to those more sublime.
The advices of the teachers, to practice metta and to win over yourself are proper and right. Reading here a discouragement to go their again: That is opposite a warrior nature and the ways even the Buddha encouraged his Monks, who where running away from spirits, to return on that place, giving them the famouse Karaṇīya Metta-Sutta as their tool.
...Because the people in that area were very pious, they invited the monks to spend the three-months rain's retreat in that grove and they even built five hundred meditation huts for them.
Thinking that there is no danger, the monks plunged into meditation with great effort. However, due to the excellence of the monks' virtue, the tree-deities who lived on tree-mansions felt their own excellence diminished. So, out of reverence for the meditating monks below, did not like to reside above them. Hence, they took their children, descended from their tree-mansions and began to roam aimlessly.
Nevertheless, roaming in this manner everyday was not convenient to the deities. Therefore, in order to make the monks leave, they created terrifying forms of demons and produced dreadful noises at night when the monks were meditating. 
Being harassed thus, the monks were unable to concentrate. Then their seniormost Elder told them, 'Friends, there are two kinds of rains' retreat laid down by the Buddha — the early and the late. Because it is not easy for us to stay here, let us go back to the Buddha.'
All the monks then went back to the Buddha and related their frightful experience. The Buddha saw, through his supernormal power, that there is no better place for them and told them: 'Monks, there is no other suitable residence for you. It is only by residing at the same place that you will attain the eradication of the mental taints (āsavas). Go back to the same grove and reside there! If you want to be free from the harassment caused by the deities, learn this protective Sutta (paritta) of Friendliness (mettā). This will be for your protection as well as for your meditation practice. Cultivate this meditation on friendliness repeatedly and those deities will not terrify you. They will definitely show you kindness.'...
Many details and how to adjust metta proper, incl. the story behind the Metta-Sutta, you find at the link, generously, compassionated, consciously given by Ven. Nyanadasana, who's Dhammic roots are maybe not that far away the place of you personal challenge.
If the heart is put right (e.g. right view), if all duties are done, even the biggest monsters will not be able to disturbe you, knowing there are no faults present in me, done all my tasks. And so you metta for them and all others will be honest, pure and for all perceivable.
Prerequisite, preparation for Meditation is always Generosity fist, then and incl. firm virtue practice. See some practical advices here in this answer as well.
Best wishes and the effort to train patient and metta, devotion, as a firm and unshakeable foundation. Fear (of unskill kind) falls for one having entered the stream.
[Note: This is a gift of Dhamma and not meant for commercial purpose or other low wordily gains by means of trade and exchange.]
I talked to the teachers about it and they said to practice metta meditation and to ask these beings to not disturb my meditation.
If these are real external disturbances (rather than internal delusions):
(i) they are not beings from another world;
(ii) they are merely minds with psychic powers, as described in the Pali suttas; and
(iii) these minds are engaged in transgressions of the Buddhist Vinaya, as follows:
Displaying psychic powers. A related rule at Cv.V.8.2 states that to display psychic powers to lay people is a dukkata. (page 266)
(iv) this type of activity is cult activity; trying to engage in mind control.
(v) in the Pali suttas, being "captured by non-humans (devas)" is one of many reasons for not reaching the ocean of Nibbana, as follows:
The Lord Buddha continued,
If that log is not caught on the near bank, it will reach the ocean.
If it is not caught on the far bank, it will reach the ocean.
If it is not submerged under the water, it will reach the ocean.
If it does not land on a small island in the middle of the river, it will reach the ocean.
If it is not taken away by a human being, it will reach the ocean.
If it is not taken away by a deity, it will reach the ocean.
If it does not sink into a whirlpool, it will reach the ocean.
If it does not become rotten, it will reach the ocean.
They also asked me to not be afraid and simply watch the fear. It did that and it did work for the time being but the fear overpowered me during the entire retreat although I am glad that I was able to make some good progress.
The fear overwhelms the mind because what is occurring is psychologically intrusive. It is worse than physical abuse because it is very difficult for the nervous system to control the psychic power sense contact; which causes loss of sleep; because psychic power is external mental energy entered into the nervous system. Because the mental energy is not created by the afflicted mind, the afflicted cannot control the energy; unless the mind is highly developed.
It is ideal to view the sense contact as 'nama-rupa' or 'a sound' (rather than as a "being"). The Buddha taught external objects are merely mind & matter (nama-rupa) and not-self (anatta). Refer to SN 12.19, which is properly translated as:
Bhikkhus, for the wise man, hindered by ignorance and fettered by craving, this group (of five aggregates) has thereby originated. So there is this group and external mentality-and-materiality: thus this dyad.
What is experienced is not "beings" but mere "mentality".
I want to be better prepared this time around when I am going back again. My question is what can I do better this time so I can be well prepared and so the fear of being disturbed again does not overwhelms me? I would like to practice meditation this time by leaving fear behind. Thank you for reading this.
Personally, I would not return to this place because, to me, it sounds like an immoral cult that does not follow the Vinaya of Buddhism.
In Vajrayana Buddhism, there are protective deities such as Mahakala and Vajrapani who are real beings evoked by Tibetan Buddhists to protect meditators. White Tara is also a protector. In order to gain their protection, you must receive a proper initiation from a Tibetan lama who will provide you with a mantra and a visualization. You should also learn how to build a proper shrine. In order to develop a relationship with one of these deities, you must do the practice that usually requires reciting 100,000 mantra with visualization in meditation. Do not accept an initiation from anyone other than a fully qualified Tibetan lama. My main practice has been mindfulness meditation in the Theravadin tradition, which I have practiced for 50 years. I have found these deities to be very effective. (I also found ordination to strengthen meditation.) I wish you well in your practice.