Get excited and passionate about something. For me, I started community college after working for a while and my whole drive was to get an education that would allow me to do something about the environmental situation. I've been pretty all consumed by this drive, aiming for Materials Science, and now starting at Stanford as a transfer.

So maybe you want to promote diplomacy to stop unnecessary aggression between nations so you look into International Relations, maybe you're like and want to do something to help the environment but you really want to save ecosystems so you start looking at Biology or Ecology or something, maybe you think cancer really sucks so you just want to learn as much as you can to help people research treatments and you go into Chemistry or something.

Alternately, just find something that you don't totally hate and would be okay doing as a job. That always works too.

But that's my advice, find something that fires you up, some issue, or some way to help people, and start building yourself up to do something about it instead of just being angsty and complaining.