This is a daily  life of someone who is in their early twenties. And trust me it is your age not you. Not much to worry about it, because as time passes, most of them relaize the value of time and will find out the purpose of their life. However, you are already better than others here, because you realized the fact that you are not doing things that you are supposed to do.

You already figured out your way. Now all you have to do is just push yourself a litte bit more. To do so, start with just one small thing that you feel should be changed. When you do it few times you will get used to it. 

"I do the mimimum to get by."

---Next time whatever it is (Work ,Assignment), tell yourself that this time "I will do something more than the minimum. Don't say you do the maximum. Just do more than the usual. If you think you had done enough to get by something, do few more....Not much; just a little bit more......After you done that, here you go...., you took your first step. Do the same thing again and again and again., and slowly you will be get used it and once you get used to something you even don't have to think about it...Just like when you used to driving, you don't have to think much how to control your sterling wheels. do you remember your first driving class? how was it? and what about now?

Only one thing for now, remember what i said, start with only one thing for now and once you get used to it, start another....You will be fine.