If you are assertive you feel free to express your feelings, thoughts, and desires. You will know your rights.
You will be willing to compromise with others, rather than always wanting your own way … and tend to have good self-esteem
And if you have this freedom you will initiate and maintain comfortable relationships with people.
As a result you will have control over your anger. This does not mean that you repress this feeling; it means that you control anger and talk about it in a reasoning manner.
So it’s good to be assertive.