Someone rudely cuts in front of your car. You could chase that person and abuse him or her. You choose not to do so, but sti ll repress your anger. Choosing your response does not necessarily make you happy.
However, you can choose to think that the person who cut in front of you may be experiencing difficulties and pray that he reaches his destination safely. Suddenly, your anger will disappear. You can smile imagining that. You can even be happy.