No, it doesn’t refer to pessimism, or living under the notion that you aren’t very good or can’t do anything well.
I saw the phrase repeated in one of the books I committed to read: What’s Your Worldview? An Interactive Approach to Life’s Big Questions (James Anderson).
As he leads the reader to make decisions defining (and critiquing) their worldview, Anderson points out positions that have self-defeating thinking.
For instance, Nihilism asserts there are no objective values—nothing is really good or bad in any objective sense (p. 75). So, ultimately nothing is right or wrong; and no purpose exists objectively for human beings in this universe. “Whatever you choose to do is just as valuable—or, rather, just as valueless—as anything else yo might choose to do.” So on what basis does the Nihilist accept Nihilism as the “better” or “truer” position? Why bother articulating it? Or living it out? It is no better or worse than anything else. (It is “self-defeating.”)
The same can be said for the skeptic or agnostic who believes you cannot know anything for sure. Does the assertion that you cannot know anything include not knowing anything? It, too, is “self-defeating.”
The pluralist who advocates tolerance and forbids exclusivity is intolerant toward those who do advocate exclusivity. They do what they forbid; their position is “self-defeating.”
The relativist who thinks all morality is culturally or individually or situationally defined still assumes there is some objective standard by which one can judge the cultural, individual or situational factors as better or worse, or right or wrong; thus the relativist assumes a standard which he denies exists. His thinking is “self-defeating.”
It is as if God has hard-wired into life logic and truth. The very means and ways we express and argue against Him prove His design. We prove only that our way against God’s way is self-defeating.
Just a thought. But one that isn't "self-defeating..."