How can I control my anger? I get angry very quickly and also cool down very quickly

Ask yourself to reflect on your past experiences. Go as far back as childhood. How did your parents or caretakers respond when you made mistakes? Were they loving? Were they gentle? Did they create an atmosphere in which mistakes were seen as learning opportunities? Did they correct you in kindness? What did you need to hear after you made a mistake? What did you hear instead? Was there an expectation of perfection whether implied or expressed outright? 

Now let's shift to your young adulthood and adulthood. Do you set impossible expectations for yourself? Do you set impossible expectations for others? Is there an expectation of perfection? What role does perfectionism play in your life? Do you feel that's sustainable? 

Remind yourself that you will never be perfect and neither will anyone you encounter. Put down that façade. You are a human "being" not a human "doing". You are valuable based on the simple fact that you are human and not based on the value your actions can add to society. Treat others with the kindness that stems from looking at them through that same lens: they are also people who are valuable simply because they are human too. 

Instead of thinking of this as difficult, think of it as different. It will be different than how you're used to treating others, but with time and practice you will have kindness, grace, and compassion ingrained in you. 

Next, remind yourself that although anger can feel powerful at times, it actually leaves you vulnerable. It means that another person is controlling your actions rather than you being in control of your emotions. You are then vulnerable to them taking you on an emotional roller coaster. Being reactionary isn't useful here.

Next, identify what is underlying your anger. Anger is like an iceberg - in the surface everyone can see that a person is angry but underneath that anger is a sea of emotions. What is the need that underlies your anger? Are you angry because you're frustrated? Are you angry because you feel disrespected? Are you angry because you are hungry? Are you angry because you are tired? Are you angry because you feel overwhelmed? Are you angry because you feel anxious? 

Anger can have many underlying emotions. This is why it's important to get to the root of your anger. Someone else who is in your shoes may not make the same choices you make even though they feel the same emotion. So they may not be able to relate to the choices, but they can relate to the emotion.

Express your emotions by being assertive. Remember that you can be assertive and polite. You don't have to be rude in communicating your needs. Remember that anger is simply a need that has gone unmet, so find what you need. Tell the person that you feel (emotion word) when they do (action here) and what you would like them to do (action here) instead. Figure out the unmet need. Take deep breaths. Take a break from the conversation. Express yourself politely while setting healthy boundaries. Follow this pattern and you're likely to succeed.