Fear of Success
You know when you set yourself goals, and it doesn't really work out. Small goals, for example, tonight you will finish all your homework for the upcoming week. The moment you set yourself that goal, you feel motivated and ambitious. You sincerely believe you can finish all the workload in a single night. I'm not saying you can't, because it is possible. But you never end up doing it or not as much as you wanted to do. The second you begin you have lost the sense of motivation and push you need to keep going. It's likely you do some or not even any work on that night. You simply end up doing it the night before, because you don't have a choice.