only attempt to paint, draw, whatever when your mind is fully at ease. If your thoughts are elsewhere you will never be happy with what you've done and in my experience this leads to dumping stuff which may actually be pretty good? If your hearts not in it then whats the point?
When out and about, never concentrate on the fact that passers by may be perplexed by your activities, its going to cause you mischief. Just ignore everything around you, because if your gonna get caught, your gonna get caught. People will sometimes suprise you though, and actually want to chat and discuss what your doing, this is a warm change and its nice to hear what strangers think.
Cleanliness is next to godliness, don't leave shit where your doing something, try and pretend it just appeared there or a least attempt to give that impression.
If a painting, image, idea is stressing you out, leave it be. Have a cuppa and an eccles cake, maybe a cigarette and come back at it. It can be torturous just to keep plugging away, building the Hulk rage. Its going to there tommorow?
Don't fear criticism. it can be good to hear if your on the wrong path, best thing is ask someone outside the life, someone real close, like your mum, or your girl/boy. See what they think, their answers or responses are going to be nothing but honest. Its the only way sometimes to see what your actually doing. Most of your friends will be too scared to say what they really think, which is sweet, but doesn't help sometimes.