By expressing the anger, by saying how you feel about yourself and your needs, you don't build up resentment against others. After you are done expressing yourself, you are ready to hug others and laugh with them again. Then you all know where you stand, you do not trample on each other's feelings, you respect each other, and you move on. It is unexpressed anger that is harmful. Too many people confuse anger with resentment.
Anger can be positive, whereas festering resentment can cause people to become murderous.
It is the things we have never said that harm us most. For then our temper becomes hair-trigger and we may explode over some insignificant item with a reaction out of proportion to the cause. Living your own message also involves an aspect of openness and humility. As a therapist, you are not seated at some remote vantage point looking down on the ignorant masses in need of help. You just do whatever is necessary, trusting that love will show what is necessary.