I have often heard people say (or atleast quote others) that the mind is what allows you to break your previous limits, the mind is what allows you to grow, and the mind is everything in bodybuilding (besides nutrition :p). I have observed that that is only partially true. One can use the mind to surpass previous limits set by the mind, there’s no doubt about that. However, the mind can not surpass itself. A mind can not imagine something more imaginative than itself, it’s just not possible. That’s how the physical world operates, you can not create something you cannot conceive.
Now I can use my mind to make my body perform more reps than last time, load more weight than last time, or do more sets or run faster. However, the mind eventually has a stopping point (until you push past it and create a new one). This is called being uncomfortable. Lifting weights until you are is a way to expand you horizons maybe a little bit. But it’s not worth putting in enough effort to just get uncomfortable, and then quitting. The real victory is when you are able to push through that discomfort, and you realize that there exists something beyond being uncomfortable.
I argue that if one is seeking the absolute largest amount of results (in terms of pushing your physical limits), the body must have the final say. The mind can push the body very far, but the body without being led by the mind can go further. This is exhaustion. This is what makes you feel like you just conquered something and grew and became a new, better person. When you no longer allow the mind to guide the body, the body will go significantly further than the mind can. This is partly because the mind operated on previous experiences, and will contrast your current workout with previous ones. Instead, use the mind to focus on the muscular contractions, or on nothing at all (if your form is very good already). This will remove the only obstacle between dramatically changing your body, and becoming a greater individual. Being able to remove the mind from the workout will cause your body to rely on it’s own guidance, and I believe it to know itself much better than the mind ever will.
You can see this as a sort of meditation, when you remove the mind from the body, the body operates under its own guidance. The body knows how much it can take, and it is nearly always much, much more than the mind would have thought. Additionally, you get to observe your body at work, operating as it knows best! This opens up much learning potential.