> using epoxy on some plastic
> two big flat surfaces. easy stuff
> sand and clean both surfaces
> warm both surfaces with a torch to remove any moisture 
> apply epoxy to both surfaces
> cures like it should
> I go to use the now fixed part
> instantly falls apart
> epoxy has all the sanding marks molded into it, no air bubbles. It just didn't stick. 
I forgot that real life is actually like and RPG and you can just roll a zero and lose for no reason.