I decided to note on a daily basis what I learned over the day. To commit to it, rather than being a note in a note book, I made it as a blog[1] on which I post daily. It is badly written and really incomplete but as it is mostly for myself, I have no issue with it.
The ultimate goal is to see what I learned over a year so I can better appreciate the progress I made, rather than only base my retrospective on feelings. It might also be useful to find what I learned but can't put the name on it, or find links to interesting things I found several months ago.
To help staying focused, I decided to fix goals and rewards. The first reward is on January 1st if I haven't skipped a single day from when I started.