You are right. David Goggins, former Navy SEAL talks about how the mind is a weak instrument and that the body is capable of much more than the mind believes.
“He would say that when your mind is telling you you’re done, you’re really only 40 percent done. And he had a motto: If it doesn’t suck we don’t do it. And that was his way of forcing us to get uncomfortable to figure out what our baseline was and what our comfort level was and just turning it upside-down.”