In respect of karma, everything good, intelligent and true that has been done by a man stands on the credit side; evil or foolish deeds stand on the debit side. At every moment he is free to make new entries in the karmic book of life. It must never be imagined that life is under the sway of an immutable law of destiny; freedom is not impaired by the law of karma. In studying the law of karma, therefore, the future must be borne in mind as strongly as the past. Bearing within us the effects of past deeds, we are the slaves of the past, but the masters of the future. If we are to have a favourable future, we must make as many good entries as possible in the book of life.
Source: Rudolf Steiner – GA 99 – Theosophy of the Rosicrucian – VII – The Technique of Karma – Berlin, May 31, 1907