Following depression at university I set up all sorts of mental checks to watch out for it happening again, ways I can gauge my mental state, all kinds of tiny little checks, specific pieces of music that (for lack of a better word) resonate with my feelings at different levels of depression, actions that I can take that I know provoke differing emotions depending on mental state, deep searching questions whose answers are telling, all these checks and indicators built up to let me know, because one of the big problems with depression is that it comes on so gradually and is so strangely shameful that its difficult to admit or even believe you are depressed and not just being a baby, and these are sure-fire checks I can use to say one way or another I am or am not depressed.
It has been a good long while since any of my checks have returned positive, but a lot of them are doing so today... so how am I feeling? I think I am feeling depressed.
Addendum:
If I had to break down depression into 3 stages of "Struggling", "Spiralling" and "Pre-Corpse" (Which I have individual checks for each stage) I would say I'm in stage 1: "Struggling".