I am assuming you are asking on ways to improve your mental wellbeing because you are dissatisfied with the state of your mind.
It is about balance. The Buddha taught about the Middle Way and the importance of keeping a fine balance. I believe you had a taste of the drawbacks from letting the mind do as it pleases i.e. the lack of focus, the listlessness and irritability. But the unspoken part about keeping to the middle is that one must have a heightened awareness so that we know when we are going to extremes. It is like riding a bicycle. Lean too much to the left or right and we fall off the bicycle.
Similarly, the Buddha advised Venerable Sona on the right tension in order to succeed in both playing the lute or in making progress in the spiritual practice. At the centre of this practice is what we are attending to. When riding a bicycle, we attend to and is aware of the tilt of our body. Using the forward momentum and the tilting of our body to maintain our balance. When plucking the strings of a musical instrument, we attend to and is aware of the sound made and adjust the tension according.
When striving for a healthy and balanced mind, we attend to and is aware of all the parts of our mind. If one had seen the animated movie, Inside Out, one will realise that the mind is made up of many voices. There is the addictive part of our mind that is always asking for more and is never satisfied. Even after watching porno for hours, when the other parts of the mind complained about tiredness (eye strain), boredom and information overload yet the addictive part still urge for more. Then, there's the realistic part of the mind that complained that it is merely acting and not real. But its voice is drowned out. Often, the part of the mind that shouts the loudest get our attention instead. Unfortunately, it is not the one that produces the best future outcomes. Many a time, the best future outcome is when all parts of our mind are actively involved in charting the course.
So don't just listen to the part of our mind that shouts the loudest or out of sheer habit. Experiment to see if there is a difference. Ignore the addictive part e.g. abstain from porno for a couple of days or a week. Is there a difference to the mind?
If we find ourselves spending too much time inside our head, are there other voices that is complaining about boredom and wanting to venture outside? Experiment, spend half a day outside be it in a busy street/mall or a quiet park. Whilst outside, don't let ourselves stay inside our heads. Observe the people around us, the young and the old, the good-looking and the ordinary, the happy and the sad. Examine the trees in the park, each has its own story to tell. In fact, the world is ever eager to tell us its stories if we are willing to give it our full attention. It can be way more interesting than the same old monologues inside our heads.
One mistake, I made, in my younger days was to objectify happiness. When we objectify happiness, we begin to see others as mere tools to achieve our happiness. We get upset when those tools don't behave as we wanted. The state of our mind is separate from the world. Realising this is a necessary first step away from the constant danger of being caught and swept away by the world.
Lastly, do not underestimate the neuroplasticity of our brains. I read of accounts of people who suffered from dyslexia and how through great efforts and perseverance, they learned to read, write and become successful. If the mental condition is not too severe, all the more we have a chance to overcome it. It's precisely the challenges in life that makes it worth the struggle. If everything is handed on a plate, what meaning is our life, what worth is it?
With Metta.