I'm in the same boat :U Commissions are extremely stressful (unless it happens to be for ARPG stuff where they get points regardless).
I haven't done commissions in ages because of this. One of the ways I used cut back stress as much as possible, was having lots of communication with customers and offering to show multiple steps through the comm, so they know what's up and so you can get input and such. More work, but I'd rather know about a mistake and be able to fix it before finishing.