I use an app called Commit, which reminds me each day of goals I set in it. Besides that I have a text file, in which I write periodically what my current goals are and anything I did each day towards those goals. I always have that text file open in a Sublime window. I include all kind of random little sub-observations such as useful links, stuff I learned or small little realizations next to those activities.
It's cool to be able to go back in time a few months and see what was occupying my thoughts back then. You can also search in it if you are having some problem again which you feel like you might have encountered before and often I find the answer there.