Making mistakes is not a sin but not learning from the mistake is surely a sin.
Analyze criticism. If the intention was only to hurt, ignore it. However, if the criticism was constructive, then welcome it wholeheartedly.
Life does not end with a failure. Single pointed focus and hard work will eventually bring you success.
Avoid making mountains of out of a molehill.
Keep occupied always. Fear of failure sets in when our mind revolves around the same problem.
Discussing problems with near and dear ones can help in alienating negative thoughts. It can also usher in new developments.