How to deal with anger?
Generally speaking, difficult emotions related to anger and anxiety can be diminished with mental clarity. Emotion itself, while educational, is either positively or negatively disruptive. We tend to love emotion if we are in love, happy, or experiencing something pleasant. But even enjoyable emotions "take our eyes off of the ball" in the sense that logic tends to be on the other side of the pendulum swing.
Seeking clarity and mindfulness is a step in the other direction. Things seem to make more sense and we usually have greater self-awareness in this sort of state. This is the opposite side of feeling anger and anxiety, which what the question was geared toward. How does one manage those emotions?
Commonly used tools include time-outs, box breathing, mindfulness, meditation, and cognitive behavioral therapy. The EMDR "Safe Space" technique can also be helpful. Add to that a list of hobbies which can either take the mind of anger and anxiety completely or assist a person in working through them.
Often, it seems that when a person is asking for help with anger or anxiety, they've already tried some of these things, and the emotions seem so overwhelming that they feel impossible to manage. And I do think that if one has as patiently as possible tried these with no success, then it's time to see a a psychotherapist for a last-ditch effort to make sure enough has been tried.
In terms of the specific techniques mentioned above, box breathing, time-outs and the "Safe Space" technique are among the most immediate short-term actions that be taken to alleviate the stress of such thoughts. Box breathing, which is sitting down and slowly inhaling four counts, holding for four and exhaling for four, can lower the heart rate and relax the body. Time-outs are taken from a source of anxiety, especially difficult conversations that provoke anger. If they are taken in agreement with another person, rules need to be set for them so that both parties accept them as legitimate. The Safe Space technique involves using patting of the body alternating on either side while visualizing a very relaxing and peaceful circumstances in one's memory.
Mindfulness techniques such as meditation take more patience and are geared for more long-range work, but Calm and Headspace are common apps for easy beginning execution of such practices. You can also find free examples on YouTube.