Agree. If you are focused upon something other than yourself, the pain appears to go away. The second you focus upon yourself, the pain can be intense. Folks who do martial arts know this. If I punched you in the face, surprising you, your pain reaction would be quite different than if we were in the ring together, adrenaline flowing, and expecting to be punched in the face. Short of being knocked out cold, you might not register the pain of getting "your bell rung" while you were actually fighting. In powerlifting, the same thing, there's a point where there is SO much pressure from the weight and your body is screaming "Stop! Stop! Stop!" and by shear will, you push through that pain. Rep after rep. Set after set. Day in. Day out. You just deal with it. If you're not in pain, you should be, so embrace it. It quickly becomes a mental process to override your body's natural instincts to protect itself.
People who have a lot of time to sit and dwell upon themselves, those "inward thinkers", and are not actively engaged in other things, I would suspect, would likely feel pain more intensely.