Looking through project docs and deciding I need to build something because I know that I have ONE of the cap values it requires on hand. Justifying the purchase of 79 components to use up one leftover.
I'm very guilty of this, especially with unusual IC's. Except whenever I order them, I always order at least one extra. It's a vicious cycle.
I keep a folder on my computer with subfolders for documents about projects I have planned (and another folder for completed projects). Currently the "planned" folder is 24 MB!

The "completed" folder is only 20 MB.

I am constantly plucking component ends out of my feet.
I build projects just because I like one of the colors on pedal parts plus that I haven't used yet.
I complete a build, spend 10 minutes with the guitar testing it out to make sure it works properly, and then put it in a drawer and start working on another build. Even the ones that sound really good! Eventually I'll slow down and spend more time playing I hope....or at least lend them to friends who actually play guitar.
And so on....