*story time*
I grew up as a very devout Mormon. Mormonism takes whatever Christian emphasis there is on free will and magnifies it greatly. Joseph Smith added a mythological story to the creation in which there was a debate in heaven about how to structure the universe they were about to create. Angel Jesus offers the plan of free will, saying that he is willing to pay for everyone's sins on conditions should they misuse their free will. Angel Lucifer offers up the plan of control, saying that he will borrow God's power to force everyone into righteousness - eliminating the potential for sin, ensuring everyone returns to heaven. God chose Jesus's plan, and he gets promoted to de facto God in order to implement this creation plan. Lucifer gets pissed and rebels. 1/3 of the angels follow Lucifer because they didn't think they would be able to succeed under Jesus's plan. They become demons as they are cast down from heaven.
So this is all just to emphasize how ingrained free will is into their theology. "No free will" is basically demonized as Satan's plan. This logic further affects Mormon perspectives on government regulation, as less regulation equals Jesus's plan, more regulation equals Satan's plan.
Growing up in this paradigm caused me to think of myself less like a biological entity and more like a divine avatar. I would abuse my body, frequently only getting 4 hours of sleep a day, because I thought that my purpose in life was to maximize my growth and potential. My body was expendable. Jesus could heal anything. As long as I harmed my body in the pursuit of good things, God would fix my body - just like he fixed Jesus's body.
So at my first professional job, I was going to work on only 4-6 hours of sleep daily. I was frequently mentally fatigued. For the first time I started to consciously bump up against empirical evidence of a lack of free will. Thinking I had some omni-powerful control over my body, I figured I could just will myself into not being tired. If I just had enough willpower, focus, and determination, I could dispel my fatigue. Day after day I tried to overpower my fatigue, but I eventually realized that I didn't have the power to do so. I lacked free will in the dimension of controlling my mental fatigue.
It seems like I eventually damaged my body so much that multiple disabilities and health problems began to destroy my career. Major backfire. This is the level of harm a "free will" mentality caused me. Mormonism didn't just make me foolish, it probably caused me long-term damage.
I'm curious if anyone else has any stories about how they might have been duped by a free will perspective and how that affected them.