i knew what i did and why i did it, two years ago, after which i never had to touch it again until now
Hahaha, true. This is why I try to keep as many notes as possible, leave lots of comments, add READMEs, links, and otherwise document what I did and why.
It's not perfect, it's often tedious, and I don't always do it, but when I come back 2 years later wondering why I set some random option, it's pretty nice having at least some hint.