It's important to keep a log of efforts, events, and ideas.
Your log does not have to be elaborate, but it's best if it is time stamped, organized, and easy to refer to.
Logs like this can help you to look back to understand issues--to know what happened, and if mistakes happen, to understand where the mistake came from and how it might be remedied in the future.
Without a log, the past has a way of recreating itself--with a log, facts hold a higher place.