I completely agree. You need to firgive those who hurt you for YOU. Once you can do that, you can let go of any past hurt of resentment. It isn't necessary to tell the person you forgive him/her as long as you find your own peace.
Yes. It is very true. Until you forgive, you will will harbor the resentment inside. That resentment is like a burning coal you intend to toss at your ex, but it only serves to burn you. Let it go. In the end you will be a happier person.