In some ways I think you're correct. Most people don't actually sabotage themselves, but run into problems.

But ... I've actually watched my wife self-sabotage. Now it's not in working on herself or anything like that, but she grew up being told that she was a failure. She was always told she couldn't finish things and that she wouldn't amount to anything. Now I can watch her start a project and start it in such a way that there's no chance she can finish it. When she starts something great and is having success, she'll mentally defeat herself. When you point it out, she'll realize what she's doing and correct it, but you can actually watch it happening and she isn't cognizant that she's doing it.

So yeah, I've actually seen it happen and watch it every day. It usually comes down to someone living up to a self-depreciating cycle started when they were young.