Trapped my own piece

Here is a position from last night's game at Carl's Jr. (g/20), round 1.

I was White and it is White's move. White is up two pawns and about to win the pawn on a4. Instead of playing the simple Rxa4, I played 19. b3? d5! My bishop is lost. 20. Rxa4 dxc4 21. Rxa8 Qd5! 22. f3 Bxa8 23. bxc4? Qd4+ 24. Kf1 Qxa1+ 25. Ke2 0-1

Lessons to be Learned:
1. Do not relax when up two pawns. Need to be alert for opponent's tactics
2. Need to anticipate Qd5 and Qd4+. Those moves surprised me during the game.
3. Need better board vision