We may unknowingly make a mistake during any activity.  After we make a mistake, however, it is extremely important to confess and purify it.  No more than a few people will willingly commit bad karma with full awareness of what they are doing.  All negative karma and moral downfalls happen through four gateways:

1) Not knowing
2) Not respecting
3) Lack of care
4) Predominance of delusion

Generally speaking there is nothing positive about negative karma, yet the fact that it can be purified is said to be its good quality.  Accordingly, with strong regret, we should purify negative karma by means of four powers.  The four powers are:

1) The power of the basis
2) the power of remedial action
3) the power of regret
4) the power of not reverting to faulty conduct

Excerpt of text written by Khenpo Karten Rinpoche, from the book Precious Teachings, chapter entitled “A Brief Explanation of the Four Powers of Purification of Negative Karma,” page 113 in the paper book, and page 121 in the PDF version.