I usually want to explode when one of them is taking too long to do something, eg. getting out the door in the morning. We usually have bags of time anyway, so I just decide to sit down and chill. After all I'm not going anywhere else at that particular moment.
Sometimes though, especially with teens, it's OK to lose your temper. There is usually a lot more at stake with teens and sometimes when you play nice, they think they've gotten away with something, or that you're a pushover. Every once in a while a raised voice stops them in their tracks. As long as you don't rant for too long; then you just look like the lunatic parent that they already think you are!!