There will always be a point where you simply snap under stress, no matter how well you rationally understand the difference between pain and suffering while being at rest, and you will undeniably suffer from the pain when that happens. It's why torture works so well.

Not to say that knowing this difference has no merit, just saying that it has limits to how much it can do. After all, reality can also hit the brain, when it gets flooded by hormones and neurotransmitters that take away your rational thinking.