I was doing pattern work in a 172. Wind changed, so the tower swtiched runways. I taxied to new runway (after a circuit in the pattern) and took off. But...(a) the wind had changed back to a direct 90° crosswind, and (b) I had neglected the checklist item for configuring flaps for takeoff. In the 172 I was flying, that's 0°. I had them at 40°. I lifted off and that wind stomped on me hard, weathervaning the 172 hard to the left, me fighting to keep it airborne with those barndoors in the wind. I was actually keeping it under control and then I made the worst mistake...I dropped all the flaps at once.

Hooo boy. Don't do that.

Instant stall horn. I pushed the nose down immediately and barely cleared the trees next to the runway.

They say accidents are made up of links in a chain. One more tiny link in this one and I'd have clipped the trees and splattered my plane across dense suburban housing.