I can understand what your saying because a while back. I loaded up the bar with 275 lbs. I was supposed to deadlift that for one rep. However, I didnt realize, but my friend who was a beginner at the time put the wrong weight on while I was drinking water. I ended up deadlifting like 300 for one rep.
That was strange to me because I prepared my body to do 275, yet it ended up being 300. The mind is a powerful weapon.