I have these posters in my office and refer to them frequently when speaking with students about frustrations and anger management.

Children [and adults] need to learn, it's ok to be angry, but how we deal with it is  what really matters.  Do we throw a tantrum- hitting others or destroying things in our path?  Or, do we take a few deep breaths, talk it out with someone we trust, and take a moment to think about our actions?  Ultimately we are responsible for ourselves, and for what we do.