I became a grownup at 23. I was living alone in a ground-floor apartment, a six-hour drive from my family and at least an hour drive from any of my friends. The apartment wasn't in a nice neighborhood. One fall night I turned on the microwave, and it went dark; a fuse had blown. When I opened the fridge door, the light was off. If I didn't fix the fuse, all my food would spoil, or at least be highly suspect by morning. To reach the fuse box, I had to go outside, walk around the unlit corner of the building with dead leaves blowing in my face, unlock the basement door and descend a horror-movie wood staircase. The light switch was at the bottom. You should've seen this basement, too: a series of rooms going all the way under the house, ceilings lowering progressively as they got further away from the stairs. Once the light was on, fixing the fuse was the work of a minute, and then I was back upstairs with the microwave going and all the blowing leaves firmly shut outside. That was the night I conquered fear.
Although zombie movies still scare the living shit out of me, so maybe it didn't work.