"Writing therapy is a form of expressive therapy that uses the act of writing and processing the written word as therapy. Writing therapy posits that writing one's feelings gradually eases feelings of emotional trauma."
Says Wikipedia.
Forgetting and letting things go is essential for your mental health.
Forget Diary is a unique diary in this aspect. Type out your most embarrassing feelings, your anger, your regrets. The mail you couldn't send, the words that should not be uttered. Type them out. And watch them go away.