Paul has abandoned all confidence in his flesh (:4-8). Even his most reputable achievements and titles in his culture he pushed aside as he 'strained' toward the Kingdom.
Here are a few things he abandoned in order to move heavenward: 1) Past guilt, hurt, shame 2) Present comfort and prestige 3) Future success' and achievements in the world. Paul 'forgot' everything that hindered his journey with Christ and guess what...he changed the world.