A friend told me that it was necessary to hold onto anger sometimes. Here’s source’s response. Blunt Force Truth: Anger is caused when natural flow is disrupted within the emotion. Anger causes harm to the person who holds it. Yet it can be transmuted to higher vibrations of emotion, allowing the free flow of natural energy. Acknowledge and let the energy flow, freeing your mind from anger’s grip. If you find yourself holding on for any reason, simply find the highest intent, and find a way to reach this highest intent with love. Works every time! 
=D