I had cooked a roast beef on Sunday, with plenty left over...since that time, I attempted to reheat with a jar of gravy and a can of Progresso beef stew, heated in the oven @ 350 degrees, of course the meat turned into shoe leather...is there any way at this point that I can cook the remaining beef down to like a pot-roast consistency, or will it just continue to get tougher and tougher????