Playing too passively
This game is a good example of playing too passively at key junctures. The passivity on both sides never really lost the game but gave up an advantage going back to equality. On my end move 16 is really bad, I can forgive myself not playing Nxb4 because of the longer string of calculation and not being sure about the resulting position but there's no excuse for not playing e5.
In the endgame my passivity cost me a slightly worse position. Then he blundered although I took an extra move before playing the winning move