I announce my projects so people can tell me how stupid I am and it makes me more determined to succeed and show them how they are actually the ones who are stupid. I guess I'm petty like that.
I feel that. One could argue that all ambitious entrepreneur types are motivated at least partly by a burning desire to prove that the other guy or “the system” is in fact the asshole.
I don't agree. True ambition is very self centered, almost egotistic. The detractors never have as much invested as you and are largely irrelevant. You don't do it because they say you can't, you do it because they don't even exist.
Shouldn't you be doing this as a positive for yourself, instead of for a negative, external motivator?
Defiance. Often a negative trait, sometimes a motivator. Learn to control and harness it.