This is what I do. It's very dry and terse but I find it useful to keep track of time spent and achievements completed. It's very easy to feel as if I've been doing nothing, whereas in reality that's very rarely true.

I tried emotional/confessional journaling for a good few years but I really didn't find it helpful or insightful.

The things that work for me include exploring my surroundings, almost any kind of creative work, napping, and talking to friends/partner.