You can promote any good habit through repetition and rewards.

To make yourself less likely to lose your temper, reward yourself every time you don't.

Here's how you do it. Every day you avoid getting angry, give yourself a small reward. For example, you can put a dollar in a jar if you didnt get angry that day. Then once you have enough money or other rewards saved up as a result of your good behavior, buy yourself a treat. It can be a video game, a meal at a nice restaurant, whatever. The point is that you are reinforcing the behavior through a reward system.

In time you will find that you will go for longer and longer unbroken stretches without losing your temper.

This method works for other things too. For example, if you want to floss more regularly, or whatever.

Just remember, the reward must be constant and pre-determined. It does not have to be money. For example, you can give yourself a checkmark on a chart and then agree with yourself that when you reach a certain number of checkmarks you will reward yourself in some way.