If you wake up each day, interrogating the world as to whether or not you're important, you, in turn, render yourself disabled. You forfeit any potential, as much as I hate that word, any potential you may have to go out and do something important or to remind any other individual in the world that they're important themselves. Wondering if you're important or capable of important things is a waste of time. It's something you need to accept about yourself, and move on. You're a human being that exists; you are therefore important and capable of important things by default. Questioning that unquestionable fact is only going to keep you somewhere you were never meant to be, away from all of the things you were. It's the biggest predator to importance that I can think of. It's also incredibly boring.
(Sometimes I like to write as the complete opposite of myself. It seems to help trivialize the neuroses.)