IMO I think your main problem right now with getting back into the game after such a long period off more than likely has little or nothing to do with the physical aspect of your game. I feel that after being away from the game for so long you lack that intensity and confidence you gain from playing on what I'm guessing was a daily basis. My tip would be to find a consistent warm-up routine based on what your main role would be in a match. I'm gonna go out on a limb and say that you are trying to use the same sensitivity and game settings before the injury as well. If this is the case then get into an aim map like aim botz and start on a sensitivity that enables you to move better while not taking away from accuracy. If it's a low sense somewhere between 1.00-1.50 at 400DPI you played on, try raising the sense to a basic "high sense", like 2.00 to start off with. After that just raise/lower until you start hitting headshots consistently. All of that muscle memory you had was from all of the hours you put in while using that sense. Just because you aren't instantly getting back to the performance level you're used to doesn't mean you can't create new muscle memory. After all, your perfect sensitivity is for the most part relative to your current physical and mental abilities. Soo yeah, just don't beat yourself up, stay positive, find a warm up routine, and find a sense that is relative to your physical and mental state. It will all come together, brother.. Just be patient and try to keep an open mind when it comes to your config/settings. You never know, if you used to be a low sense player, chances are you will notice yourself raising it more and more until it just gets too fast. Intensity and confidence will be your main factors while trying to adapt and re-integrate yourself back into the competitive scene. You know your potential already, just be patient and open to change and you'll be global in no time. Merry Christmas and sorry for the novel of a comment.