The best thing is to get started on those long-term projects. Cut them up into smaller pieces that are easy enough to do. But first, relax. You need a distraction. I find that the most distracting things are friends, food, and fun. Better in combination.
I can get really cranky after a few days alone. And I go to school, see my classmates, and poof! my anxiety has decreased considerably. I like to go on dates (with my dad usually) and eat at a restaurant. If these are not options atm, there is still Uncharted Waters 2: New Horizons. Haven't played it in a while, though.
I've started going to gym last month, it's done wonders for my mood. Sure, I lose at least a couple hours a week, but I gain much energy. And for the time in gym, I think nothing but happy thoughts. Affirmations. Visualizations of a good future. A natural high. If I can keep this up, I won't ever have to smoke or get drunk.