You will no longer be at home, surrounded by your friends, having all your needs taken care of. People won't worry if you came home the last night, won't care if you got attacked, didn't eat anything, or didn't get any sleep. This is what makes college difficult, and unless you have been living by yourself for a while, the amount of things you find yourself worrying about can be overwhelming. Simply, you will be on your own - and that takes a while to get adjusted to. Knowing how to 'work' the system helps you to know when to study more, how to approach a problem, and how to deal with 'the world' in general.
College is very little about the schoolwork - it is about getting used to dealing with the world.
Schedule your time. It is really hard to do, but schedule time during the day when you are going to do your schoolwork. Not all your time, in fact, not even most of it. Just a little. It will help eliminate the overwhelming feeling of 'being behind'.