When you start drinking something like unsweetened tea, initially it's almost unbearably bitter. But as you drink it long enough, it feels less and less bitter. It didn't get any less bitter, you just impaired your ability to sense this kind of bitterness.

I wonder what happens with muscle soreness. Do they get actually get less sore after consistent exercise? Or do you just blunt your nervous system into not detecting chemical signatures of the damage? I'm guessing it's the second case because people here are commenting that after exercising long enough you can still have gains but no pain of muscle soreness.