Just realizing that stuff won't get done automagically.
Some problems will actually solve themselves if you ignore them long enough, but some other will come back and bite your ass really really hard. Since you can't usually predict what case will it be, it's better to handle stuff yourself.
Long story short: there's no easy magical solution, life is hard and work expands to fill al the available time. You have to sit down and get shit done.
Corollary: I've also learnt not to take commitments that I'm not 100% sure I want to (or can) go through till the very end. You don't have to delay stuff you don't have to do.
Corollary (2): it's fine to drop stuff, especially stuff like side project or personal stuff. In a work setting things are a bit more difficult, but saying "I am having trouble meeting this deadlines, please let's re-discuss it" or "I am overloaded, you'll have to assign this task to somebody else" is generally better than delivering two months late. Good managers appreciate this.
