Why do I always forget the rules I set for myself when doing art-related things with others? I'm seriously breaking my own rules left and right here.

I keep promising I won't do commissions except for real money, then I toss art at people on Wajas.

I keep saying to myself that I need to stop looking for trades when I've got requests to do.

I keep entering contests even though I told myself I wouldn't do "paid" art unless I knew I would actually be paid for it.

For those of you who set rules for yourself (not just in art, but in anything), how do you enforce them? How do you make yourself keep the promises you make to yourself?