'knowledge silos' in a one person team are real: Me today and me from 2 years ago when I set a thing up are different people, and I don't remember that any more than a team mate in a multi-person team would know it. This is where 'professional' approaches can help considerably: using 'standardized' stuff, instead of bespoking everything (even if bespoking is much easier), or making sure you write a TON of documentation for anything you don't do daily...
I'm a fan of the documenting everything even on stuff I wrote and maintain for myself. Because, like you said, old me was way smarter than current me. When he was writing this code, he had the domain space modeled in his head better than me now, 2 years later trying to fix/maintain something.
