Ask HN: How do you restart a coding project after vacation?

Imagine you are coding a fairly complex payment system with 6 or so classes, invoicing, payment confirmation, email messaging, due date tracking, etc. Memorial day comes and you leave your code as a series of half completed read and write methods, getters and setters, and some buggy calculations, briefly commented. When you come back, you are at a loss on how to restart. This is what happened to me and it's taking all day to get my head back in to it.

How do you come back to a coding project after being away from it for more than a few days?