Take notes of everything you do -- a) writing might make it easy for you to remember about stuff, b) your brain is probably not big enough to hold it all.

Continuous integration

Pin all of your dependencies, always! -- you don't want stuff to break even though you did not change anything.

Maybe schedule your jobs to run every Sunday night, and in there, feel free to break your dependencies loose -- so you know what's coming should you have to upgrade some of them.