Yep, been there. With the partying/sleep issue I found a big help was putting on a favourite movie to fall asleep to. I know that's the complete opposite of what most sleep hygiene advice recommends, but I found if people were partying in the corridors and stuff I'd just lock my door and zone out to the movie and I'd fall asleep.
What to do to stay mentally positive is a funny thing because its very personal, but I'd recommend whatever you do make it something internal that relies on nothing but you. So, for instance, for me it's reading. If I have a favourite book I can get into almost anywhere and it lets me switch off. Music is great too. I think the key thing is that it should ideally be something utterly separate from study, work or training that is done purely for enjoyment. My favourite books helped me through some shitty times.
When you're older, it'll probably be family - it doesn't matter how tired I am or how shitty training or work were that day or week but if spend time with my other half and the little one everything is ok again. Hell, if college isn't too far from home, it could be just going home for an hour. I know here in Australia we keep seeing a bunch of our top young rugby players switch teams to be closer to home and that often sees them perform much better.