Motivation, focus, discipline, there's a perception that these things are innate, that people who are disciplined focused and motivated were born that way, but they weren't, everybody sucks, everybody starts out terrible, every maestro started out not knowing how to play an instrument, every artist started out drawing lopsided stick people.
Having the discipline to sit down and practice is a learned skill, it's like writing your own user manual, you learn your own patterns of behavior, what to do and what to avoid.
For example I keep my fridge stocked with fruit and leafy greens because I know if I'm hungry and healthy food isn't immediately available to me I'll walk down the street to a fast food joint. When people ask me how I have the discipline to eat healthy when there's three fast food places just down the road I tell them it's because I have no self control. I need to have healthy food ready to eat and at risk of going off and I cannot allow myself to eat out because I know if I do it once I'll do it twice, and then I'll do it again, and then it'll become once a week, and then it'll be every other day.
Likewise I very rarely buy games, because I love games, if I have a new game to play it consumes me utterly, every waking moment, until I'm satisfied I've experienced everything it has to offer me. This is why I cannot play MMOs, I know once I go down that road I am never coming back.
The commercialized world we live in is designed to undermine our impulse control, I don't own a TV, I can't be around a TV, because if there's a TV in the room I can't help but watch it, I have to consciously tear my gaze away and go for a walk.
I don't mean to underestimate your challenges AK, you probably do have some kind of disorder which is undermining your efforts and your living situation only makes it harder still. But there's no way to rationalize your way out of the problem, you can't argue with it, even if the whole world agrees that it's unfair you there's still only one way out. You've just got to seize control of yourself, it may be a long road, it may take years of tiny incremental improvements, but there's no other way.