I used to use Moodscope to record daily subjective ratings in some key areas, like whether I felt "strong" or "productive" or "powerless" or "scared".

The process of entering the data about myself each day actually made me significantly more depressed, because it was like a constant reminder of how depressed I was, and how the external circumstances that caused my depression weren't changing (even when I was doing all of the things I could do from my end, like exercise, see friends, listen to music, and so on).

So we should keep in mind that this sort of thing isn't a panacea. In some cases, at least, it could make things worse rather than better.