The way a believer is tested in this life.
Allah سُبْحَانَهُ وَتَعَالَى will certainly send someone to test you. They will mistreat you, therefore show patience.
For restraining yourself and controlling your anger, Allah سُبْحَانَهُ وَتَعَالَى will hold back His punishment.
The believer's heart will be content on the day of judgement if he controls his anger.