Hey Madisgram,
I do this. I carried it on from when I 1st saw Psych. I find it helpful now but to begin with I didn't "get it". I couldn't see a pattern. But now I am finding I am seeing myself noticing mania/depression/normal moods quicker than I use to.
Every night before bed I do mines. I write the date, how much sleep I have gotten, if there is any issues with sleep, my mood and if there are issues with it, what I have done that day as I know I am prone to not doing things when unwell and also other info which is eczema broken out again, side effects that have resurfaced, when I got my period to see if there is a hormonal thing happening. I also write if I think I have been hypomanic etc............. This is all in a colour co-ordination scheme. Which I have stuck to. I started it 1 night and when I saw Psych he thought I wouldn't carry on with it as it was a "spontaneous" thing to do. But I have done it for 9 months now