Clicker Training if You are Angry or Upset?

I'm sure that professional clicker trainers have heard it all, but I must admit I was taken aback by a recent email I received in connection with my website on positive methods of dog training. It read:

Hello Rosana,

    May I ask if the clicker is only used to reward the puppy?  What about if I am upset or angry?

Visions of a furious trainer clicking furiously came unbidden into my imagination! Click, click, click, click...

But when I re-read the email, I realized that the questioner was simply at a *very* beginning level of understanding the principles of clicker training. I wrote back that when you are angy or upset, you should take a time out for yourself from the training, till you can collect yourself, because you are not likely to make the best choices in communicating while you are fuming.

I also replied that the clicker IS only used to signify approval of what the puppy has done.

But it did get me to wondering... how have others handled it when they get annoyed at a dog or other animal while training? It probably doesn't happen much, but if you have had an experience of this sort, please share how you dealt with it in the comments!

 Thanks!