1. a person’s state of mind seen in terms of their being angry or calm.

   “he rushed out in a very bad temper”
2. the degree of hardness and elasticity in steel or other metal.

   “the blade rapidly heats up and the metal loses its temper”

So I would say that temper is a very important part of our being and makeup but the quality of our temper is key here, I think.
We can have a very good temper or a very bad one. We can work on our temper and learn to understand how and why it works and from this develop a better temper-ament.

For example having expectations of others not being fulfilled can cause us to lose our temper. In this way we could substitute hopes and desires for expectations and learn to reduce getting angry or lose our temper.

Or being shocked by a person’s behavior seems to illicit an angry response. When all we have to do is question why we should be so shocked by such actions.

As a verb temper means:

1. improve the hardness and elasticity of (steel or other metal) by reheating and then cooling it.
2. serve as a neutralizing or counterbalancing force to (something).

   “their idealism is tempered with realism”

   synonyms:moderate, modify, modulate, mitigate, alleviate, reduce, weaken,lighten, soften “their idealism is tempered with realism”

 We can use experiences around us to temper our behavior or temper.
This is an ideal way to desensitise oneself or our temper to allow us to stay cool
and not to lose our temper.