How to Not Get Angry (Part Two)
In Tanya (Epistle 25) the first Lubavitcher Rebbe explains, that when a person is steadfast in his belief that any and all harm comes from G-d, then he won’t get angry. Because although the perpetrator, who freely chose to harm him, is responsible (and subject to punishment) for his wrong choice, nevertheless the harm to the victim had been preordained in Heaven. And G-d has many messengers to fulfill His decree.
Furthermore, in that very moment (that the perpetrator hit the victim), G-d gave him the ability to do so, since He constantly enlivens the entire world and keeps it existing. And if G-d would have withdrawn His life force for even one moment, then the perpetrator would not have been able to do anything.
(Sometimes though, a projection of anger is called for; for example, if it can be instrumental in persuading people to do G-d’s will. And that was the reason why Moses occasionally showed anger.)
The above is just one example of how belief in G-d is beneficial not only spiritually, but also physically and in our relations and interactions with others.