Anger can be useful - if for example something makes you angry and you take that energy and do something positive with it. Activism for example often comes about when people have become so frustrated with what is going on they become determined to fix it. In that case, you are taking anger and using it for something constructive. We tend to have the mistaken impression that anger is always negative - that's not always the case. It can be - if it morphs into rage or the need to yell or insult people etc. that is not constructive anger, it's a temper tantrum and it is destructive anger. In that case, you need to turn your anger around and do something positive or solve a challenge. Complaining, arguing and getting mad doesn't solve anything.
If someone is the source of your anger - for example they are emotionally abusive or angry themselves, move away from them and find healthier people to be around. People who allow their tempers to run away with them lack self-control and they'll simply drag you down with them. Walk away from destructive anger when nothing else can be done, otherwise, find a way to make it into something positive. We always have a choice when it comes to our actions, every day offers new opportunities to make different choices so there's no sense in staying angry :) instead - get busy!