It's the same for me to bro. Im not for sure, but i think it is because our muscles are used to the abuse and can handle much more. If you dont touch any weights for a year then hit the gym your muscles are going to be in pain for the next several days.. Maybe try taking a week or so off. You may feel refreshed when you come back. As far as not getting as sore as you used to.... not sure. thats just my best guess.