As everyone is entitled to their own opinion to a question of this nature, let me first say this. Now I recognize that they’re both forms of conceit. If we learn the proper use of conceit: the confidence that, yes, you can do this; other people can do it, it’s something human beings have done—you’re a human being, you can do it too. Once you’ve got that amount of conviction, then it is time to drop the “you,” drop the “me,” the “I,” and then set to work. That right there makes it a lot easier. And this way you become your own best friend.
Being overly optimistic creates a turbulent mind, and in this Dhamma path it is important to calm your mind. Overly optimistic may fuel this “optimism bias” and specially in meditation takes you off base. An optimism bias, if its expectations are not met, its absence can signal anxiety or depression, its pessimistic opposite. The Buddhist term for this is Uddhacca-Kukkucca.
Many are the obstacles which block the road to spiritual progress and uddhacca is one such. Uddhacca is a Buddhist term that is translated as "excitement", "restlessness", etc. Here I have to remind you that uddhacca is not the same as what we mean by “restlessness” or “agitation”, used in conventional language. Even when there is pleasant feeling, for example, when we are attached to a quiet place, there is restlessness, uddhacca, which arises together with lobha-mūla-citta. We may think that we are calm at such a moment, but we have actually “mental excitement”. In the Theravada tradition, uddhacca is defined as a mental factor that is characterized by disquietude, like water whipped by the wind. Uddhacca or 'restlessness', belongs to the 10 fetters (samyojana), and to the 5 hindrances (nīvarana). It is one of those 4 mental factors inseparably associated with all unwholesome consciousness. Uddhacca is a close friend to moha (ignorance). Uddhacca spreads and disperses and wanders around. It is said to be like throwing of a stone into a heap of ash. In its presence, citta becomes restless and upset.
The person who develops belief and confidence in Satipatthana will not be in a hurry. Also he will not be lazy. Many people have this indecent hurry. They are in an unnecessary hurry. That is why they try to practice for hours at the beginning itself. Such a person is in an unnecessary haste. That unnecessary haste is due to impatience. One who has trust in Satipatthana or has confidence in it is not in haste. What does he have? Patience. The nature of one who is pleased with Satipatthana, who trusts it, who understands it becomes patient. Patience arises in him. Why does he have patience? Why does patience arise in him? Why is he not in a hurry? Because of confidence. What is his confidence? It is the unflinching confidence in the Triple Gem.
Being your own best friend is good if you can manage it. Conceit is an attempt at having self-worth probably as compensation for being unloved as a child. The need to be conceited is a tragic situation that is very difficult to unlearn. Being overly optimistic or overly pessimistic may or may not be caused by conceit, but it is caused by ignorance (lack of information). Real confidence comes from knowing how a meditation actually works. For those of us who have grown up in a culture that values meditation, confidence in meditation comes easily. But, for those of us who grow up with a high regard for Western science, there is a need for an explanation that is not provided by Buddhist texts. I have recently written a book on "How Mindfulness Meditation Works." The explanation I suggest is that the Bodhicitta provides "safeguards" that eventually correct mistaken beliefs, wishes, and emotions, by seeking a better versions of the mental actions (karma) involved. The Buddhist mindfulness meditation accelerates this innate process of correcting attitudes that undermine our ability to be attuned to the wisdom of the Bodhicitta. The traditional way to deal with a hindrance is to take note, "I am experiencing conceit," and carry on meditating. "Dropping" the "you," "me," and "I" is based upon a misconception that these concepts are hindrances to Enlightenment or to a true understanding of the mind. The reality is that every concept has meaning in terms of the frame of reference, representation of reality, and/or the past experiences of the person using the concept. By questioning your concept of "me," you do not come any closer to the Buddha's concept of "me."