Former Athlete, Out of shape

I think getting back  to your "Playing weight" as a former athlete is a lot harder than  the plain jane goal of simply loosing weight. When you were used to working out hours on end and eating anything you want because you had flash spped metabolism. Fast forward 5, even 10 years later that's so not happening. Where did all my energy go? My stamina? i can barely get through one hour of working out. or i get uper pumped on pre- work out and go squat crazy.i start watching workout videos and all of the sudden i feel like the Hulk. then the rest of the week goes by where I'm too sore to get off the couch. You feel me ?Learning the right pace to get back in the game is the biggest problem.