Some people are more easily angered just as just people get more anxious in particular situations. The brain reacts faster than we can rationalise and so BOOM we blow a fuse. To change this, it takes time. CBT helps. Just as if you start learning painting, you go for regular classes so in CBT you go regularly. Second meditation e.g. mindfulness is helpful. Start with 5 minutes a day. Initially it's better to do it under supervision. Basically it depends how much you want to change. And how much effort you are willing to put in.

What you are describing sounds like a normal scenario. There is nothing wrong in being upset and angry occasionally when it is justified as anger has got some beneficial uses. However you seem to not like feeling so which may indicate you may need to find alternative ways of letting others know you are angry.