To be honest, this is not an easy question to answer. But I’ll give it a go and hopefully you’ll find something useful.
For me, drawing is like therapy. I think a lot. About all kinds of stuff. A lot of negative stuff too, to be honest. What usually happens next is that I start making up an image in my head. Sometimes that image is more clearer. Sometimes it’s fuzzy / blurry. What I try to do after I’ve had this image in my head is to draw it as fast as I can. If I wait around for it to be “clearer” I often lose that little spark that makes me actually just draw.
As I wrote earlier, I see drawing as therapy. In order to stay sane, I draw. It heals me. And when I draw, I get this awesome feeling. It’s not really happiness, but more this rewarding feeling of accomplishing something challenging. So you could say I’m addicted to drawing. It’s my kind of drug.
So to answer, how I decide what to draw. I guess I don’t really decide. I just need to do it, to make it through the day. Then of course, sometimes I’ve just had it with my weaknesses and decide to do a lot of studies to improve on certain areas. For example this January, I drew one page of hand drawings / studies everyday for 31 days in a row. That, in my opinion, has opened up a lot of possibilities for me making characters feel more real. Which has just made me want to keep experimenting with new things.
Wow, I’m really vague here, aren’t I? If you feel like what I’ve written above doesn’t help you, you could always try to do one of those “draw-everyday-for-x-amount-of-days” challenges.
I wish you productivity and progress. Stay awesome!