Physical fitness is not the same as feeling good. Cardiovascular fitness, body composition, flexibility, muscular strength and endurance, speed, agility, balance, coordination, reaction time and power must all be considered.
Being physically fit means you have a healthy BMI for your age, good cholesterol, healthy blood pressure, etc. Some people who are skinny think they are physically fit becuase they are skinny but the truth is they are not. If you do not excercise on a daily basis or at least 3 times weekly it is hard to stay fit.