You decide to change profoundly and give up crime and drugs... how do you think your druggy criminal friends will respond to that? We all know it's harder to give up any bad habit, like smoking, when we spend time with people that smoke.
One friend uses the analogy of crabs in a crabpot. If one did figure out how to climb free, the others would pull him back. Changing your life affects the homeostasis of all those around you. Maybe they don't want to live with the constant reminder that if you can change so could they. Maybe it's darker and they want you to fail so that the part of the brain that's afraid of all change can point to you as an example and keep from trying at all. Maybe...
But there are other crabs in your own mind, things that pull you back. I'm watching two people right now that have made huge gains and it looks to me like they are about to lose it all. That's what has me thinking. But in small ways, we all self-sabotage to prevent change, including success. Some write and don't publish. Everyone has great ideas that they don't try to produce (why have I never got around to substituting the peanuts in a Snickers bar for coffee beans and sold them on college campuses?)
Everyone, with just a few minutes thinking can come up with a plan to make life better. Profoundly better. Almost none will ever write down the plan or execute the steps. Those that do have found a pair of super-powers, planning and execution. But most won't. Crabs in the head hold them back. "That's for special people, not you." "You'd just fail anyway, it would be better not to try."
The crabs in our head hold us back with whispers, not claws.