he feels guilty about Pietro's death. feels like it's partly his fault. he should have died instead. and he probably thinks Wanda hates him for that, so he tries to show her how much he's indebted to her brother and how much he loves her and she understands and accepts him as her honorary adopted father.
Clint probably was tree #3 in the school play, but let's be honest, our fandom would so watch that.