Is it because you got old, or because you are out of practice? It takes about 3 weeks to get razor sharp playing it 8 hours a day then I'm pretty good again. Even in my old degraded form I'm still way faster than most young dudes in their prime, but I always had super human twitch reflexes. Its true reflexes degrade, but somehow I'm stronger than ever and play guitar better now than in my 20's. If you practice, you get better at anything. I quit playing competitive multiplayer because the stress of it makes me hot flash. My ears turn beat red and stay that way for hours afterwards and its pretty uncomfortable. But I'm super competitive so I take getting fragged like very seriously, so as soon as I'm in it, my pulse is racing and its like a weird high. I used to play quake 8 hours a day, 16 hours on weekends I loved it so much. Now I just play skyrim because single player games don't stress me out. 7 Days stresses me out sometimes, but its fun.
Hell putting on headphones to make videos does it too I need a pair of ice pack head phones lol.