Fit Happens.

There are many health related components associated with fitness... Along with fitness comes things like speed, endurance, flexibility, agility, better breathing, lower blood pressure, muscle strength, and the like. Not only does it improve your physical state, but your mentality benefits. Studies have shown that when people do physical activity, they're able to think clearer. It also makes you feel better when you've accomplished something physical. And like I said before, you get the endorphins which contribute to a good mood. To be physically fit means to to have all the things mentioned above. It means to do what your body is physically capable of. Like Billy said, it looks different for different people. Know your body and it's limits, and then strive to do your very best in exercise.