Do we act as horses or mules?

There is a story about the different behaviors about horses and mules which inspire me to change myself.

Whenever there are fierce animals attacking, horses would put their heads together inward, and using their combined strength with their legs outward hitting their enemies. Mules on the other hand, put their heads outward and butts inward, using all their strength hurting themselves.

When dealing with problems, do we act as horses or mules?