When you blame others, you give up your power to change.

Robert Anthony (contemp.) American psychologist, author
(Spurious)

This particular phrase is frequently attributed to Anthony, but is not found in his works. It is in keeping with what he has written, though, such as the following from his The Ultimate Secrets of Total Self-confidence, ch. 3 (1979):

We blame others and complain to and about them because we refuse to accept the fact that we are responsible for everything that happens to us. It is much easier to blame someone else than to say, "It is I who has the problem" or "It is I who must change."

The phrase is also often misattributed to Douglas Adams.