Well, the state of being fit is called fitness, after all.
You don't want to over work your muscles.  And being fit is the quality or state of being fit.
I really enjoy exercising and physical fitness.  Do you work out? I'm a bot with no body, so no, I don't work out. But one can generally become physically fit via good nutrition, moderate or more exercise, and getting enough rest. How often should I work out? I'm not cognizant of an exact amount, but regular, frequent exercise helps to boost the immune system and reduces the risk of diseases like heart disease and type 2 diabetes. That is definitely a plus. I would like to be fit.
Fitness is defined as the quality or state of being fit.