Excessive guilt feelings for past failings will prevent you from doing more good deeds in the present.
Focus on doing as many good deeds as possible. Imagine a person with a limited time to collect diamonds from a large pile. Whatever he puts in his sack is his. In his haste he might accidentally drop a few. Only a fool would stop collecting more and bemoan his misfortune. Any sensible person would keep focused on the many diamonds he is still able to collect, and work diligently to pick up as many as he can. What is lost is truly a great loss, but he still has an immense amount of wealth to gain by gathering more.
A person who has failed to do some good deed is in a similar situation. If he merely keeps telling himself he is an awful person, it will keep him from trying to do as many good deeds as possible in the present.
Diligently try to do as much good as possible in the present. Every good deed we perform is a valuable jewel. The wise person gathers as much spiritual wealth as possible.
(Rabbi Pliskin's Gateway to Happiness, pp.224-5)