I had my first quarter life crisis at 18, when I came to grips with the fact that I had accomplished nothing in my life so far, as evidenced by my lack of good college admissions - I graduated only 2nd in my class with just a 1500 SAT, which isn't good enough for top schools.

Unlike OP, however, it was less of an aimless drift and more of an aggressive, angry depression. Had another one at 20, when I realized that not getting into a FB internship would probably set me back permanently from my goals.

Now I'm 24, work at Amazon and widely considered a disappointment to people in OP's social circles. The pain has waned a bit, but the crisis is just constant now, like the roar of an engine on a long airplane flight in coach. Eventually the discomfort of the resting your head on the window and the anger you feel at the people with lie-flat seats paid for by Google and Facebook overpowers the rest.