People add "my friend" to the end of a sentence sometimes. It's mostly men who do this when talking to other men.

Some situations in which you can add "my friend" to a sentence include:

• When you're expressing your sympathy for someone:

  I understand exactly how you feel, my friend.

• When you're threatening or warning someone:

  I wouldn't do that if I were you, my friend.

This is not a very common way to end a sentence. It's more common to use someone's name or a label like "man" a the end of a sentence:

I don't know, man.