> I'm always thinking about "Can I (or anyone) get back into this easily 6 months from now?"

As I age, my memory is getting worse and worse and I realize that quite clearly. Therefore, I always try to write documentation as I'm writing code, so that I can remember why I did something. It helps a lot so that 6 months later, I can do exactly that... but I also know that anyone else looking at my stuff will also realize why things are the way they are.