Some more things I've learned -
If/When offering to make a quilt for someone - be specific about what you are willing to do. I was thinking about making a couch size quilt - about 60 x 80 - and the person wanted a king size quilt - to the floor, no less! We compromised with a quilt that covers the mattress and dust ruffles.
I've learned to be aware of the replacement cost of the items I'm making.
I have also learned that it's okay to say "no" - in most cases, a "no" with no further explanation seems to be the most effective. Sometimes I have to say "no" to me when I think I want/need whatever.
If someone specifically asks to have a quilt made - would they be willing to trade their professional expertise hour for hour with what it will take you to make a quilt? I don't care if the person is a $1400/hour lawyer or a $8/hour whatever pays that - my time is valuable to me - and my skill level is high. Why not value it properly!
There will be things that are so-so at best. And some things are duds. I still have not come up with a good way of dealing with the duds.
I mostly write them off as "learning experiences". Sometimes learning how not to do something is as valuable as learning how to do something.