Part of it for me, I think, is mental. When I grab a club from someone else I tend to focus a little more on mechanics. Sometimes maybe I've told myself, "I can't hit this club as it isn't what I think is ideal for me" or "this has to be better than what I'm getting out of my clubs". That little mental mind game produces a few good shots. The new club arrives and after a few rounds that mental edge erodes and habits return.
