All my life I've been praised for my alleged intelligence,

File: fantano_2014.jpg (244KB, 2048x1386px) Image search: [Google]

244KB, 2048x1386px

All my life I've been praised for my alleged intelligence, been called Mensa-smart, scorned for my book smarts that absolutely do not compare to another's street smarts, but I have never felt more than merely competent in areas I was told to learn.
Whenever I try to learn something new, I either get frustrated with the tediousness of the beginning or overwhelmed by the enormity of the concept, and end up giving up and getting depressed because I did so. I second-guess what I do know, and will often underrepresent myself in a way that leads to my rejection in areas that would have the potential to challenge me.
I have become stagnant in my volunteer job because I didn't feel confident to pick up a real job after years of wallowing in self-pity after high school, and now that this position has run its course I find myself in need of a breakthrough lest I find myself in bed for weeks on end once again.
The people I know aren't any help: they think I'm Einsteinian for being able to pick up mail merge in a day, and I couldn't bring myself to ask anyway out of fear of sounding pretentious or pathetic.
Ending ones life because one can't play a musical instrument without taking time to thoroughly learn it first is nonsense, but I can't seem to find purpose in life, and can't bear to live without it.