Agreed nin. Anger when you discipline is a VERY bad thing. This is one of the things that leads to abuse. If you are angry over something your kid did, put yourself in time out. Wait until you are clearheaded and are thinking levelly again. Think through an appropriate punishment. Dont re-act out of anger.
Especially if you have temper problems.
The one time I remember my dad losing his temper at something I did and cursing me is the one I harborerd resentment at for the longest time (and that wasn't even physical discipline). He doesn't really have a temper problem, and it happened only once, and I'm a pretty strong willed guy.
Heck not even when I went and cut every single wire I could see or reach on his motorcycle (including opening up the seat to get at the stuff underneath) did he lose his temper. This was when I was really young, 6 years old or so. I think I had just discovered the wire cutters. That particular time we both worked for a couple years afterwards fixing it. That is a great example of the punishment fitting the crime. And working together in fixing it helped in bonding, and helped teach me about electronics.
It was when he reacted out of anger that ONE time for some other thing that I harbored resentment.