Anger is a normal human emotion. It's hardwired into the human species, and therefore one of the universal emotions (along with happiness, sadness, fear, disgust, and surprise). It's unavoidable.
It's also useful. Anger serves an evolutionary purpose: it motivates us to respond protectively to perceived threats. While fear tells us to respond to threats by fleeing, anger tells us to respond to threats by fighting. Provided that we fight effectively, fighting is much more likely than fleeing to prevent the same threat from happening again. (Any child who has been bullied will tell you this: as much as we admonish them to walk away, the bully rarely stops unless the child fights back).
Of course, fighting with fists (or other weapons) is not considered appropriate in our culture (it's called assault, and illegal). I'm using the word "fight" metaphorically, here. We all need to learn to express our anger in ways that are constructive rather than destructive, ways that protect ourselves from threats without threatening others. However, the biggest barrier to learning these skills is our own discomfort with anger. It's unfortunate that so many of us were taught in childhood that anger was not ok. We may have been told it was wrong, something to feel guilty about (because we were scolded for anger), or we may have been taught that it was dangerous, something to fear (often by witnessing adults' uncontrolled anger). As a result, we may avoid experiencing our own anger, often by suppressing/internalizing it, or ignoring/denying it until it escalates into rage we can't ignore. The former contributes to depression, anxiety, self-injury, eating disorders, and addiction, while the latter contributes to aggressive, explosive, and destructive behaviors.
Neither of these strategies works very well as a long-term solution: they don't resolve whatever situation triggered the anger, but do lead to painful consequences. The answer? Become both familiar and comfortable enough with anger to notice it early and cope with it actively. That means recognizing the physical and emotional signs that we are becoming angry (irritable, annoyed), calming our bodies with breathing, relaxation, or exercise, recognizing and reframing unhelpful or distorted thinking, communicating directly and assertively, and engaging in problem solving with an open mind. Of course, this is easier to say than do, and does take some time and practice, but is well worth it in the long run!