Bark and Bite!

My wife purchased this sign and I made it very clear that it does not refer to me! I mean, how could it?
I have been very busy invigilating during this busy exam period and I always take the time whilst the students have their heads buried in the exam paper, to peruse the quotes etc on the classroom wall. This one I liked:

Commitment - Either you do or you don't, there is no in-between.