Words once spoken can't be taken back. The words now carry your name.
Often, we speak hurtful and insulting thing to others. The arrow has hit the heart. The heart is bleeding. The damage has been done.
To undo the damage is not easy. You may sincerely regret your words. But will the other person believe in your forgiveness ? Harsh words leave a permanent scar. Memories don't disappear easily.
If you can't be kind, then be quiet.