because you’re trying for the impossible.
once you accept that you’re not going to be perfect and sometimes you’re going to mess up, you’ll have less pressure weighing on you. thus, you can use that energy to spend more time with God, and the more time you spend with God, the more of His goodness and love is within you. so if you think about it, accepting you’re going to fail makes you not fail as much. it’s a win win. :D
stop promising Him things and just accept His promises instead.