An excerpt, a beautiful excerpt
The bottom-line of self-discipline is peace of mind. Peace of mind because you consistently do what needs to be done and have developed the self-discipline needed to let go of the negative events that happen to you - forgive and forget - and focus your energy instead on taking responsibility and moving forward. "Discipline yourself to stop justifying your negative emotions by continually rehashing what happened and what the other person did or didn't do." Tracy adds, "Your ability to achieve your own peace of mind is the true measure of your success and the key determinant of your happiness."
- from an article whose title and author, I already forgot