What do we do when we've broken a precept? How should we proceed in our practice when we have broken some of the five precepts? I am anguished over this unwholesome behavior and the negative karma I created. Ajahn Brahm talks about self-forgiveness and the Buddha in the Sankha Sutta (the Conch Trumpet Sutta) talks about waking up from unwholesome behavior by refraining from such actions in the future. And of course, there is the story of Angulimala, so there are some examples in the teachings of people waking from patterns of negative karma-making. I suppose the only way to proceed is to maintain the precepts, deepen my practice and strive to create wholesome karma?
Don't regret or repent! That is bad Karma. What you need to practice is Samma Vayama(The right effort) of the noble eightfold path.

The effort

(1) to prevent the arising of unarisen unwholesome states;

(2) to abandon unwholesome states that have already arisen;

(3) to arouse wholesome states that have not yet arisen;

(4) to maintain and perfect wholesome states already arisen.

Take the triple refuge and the five precepts every morning to remind yourself. Then at night, before going to sleep, reflect on the day's activities and see if you broke any precepts or if you can improve with Samma Vayama and try to do better next day.