If you have cardiovascular endurance, then it means that you have healthy lungs. Having healthy lungs, an a healthy vascular system in general, means that you have a better ability to deal with stress and avoid illness.
If you have muscular strength, then it means that you have efficient ADLs. This means that you are able to carry out all your required daily activities without becoming short of breath. If you are unable to do so, then some simple weight training should be able to fix increase your daily activity level.
If you have muscular endurance, then it means that you have linked the connection between the first two components of the 5 basic components of physical fitness. This means that all of your muscle fibers are being worked and you are healthier than those who have not reached this level.
If you have a good body composition, then it means that you will most likely avoid the negative effects associated with a poor body composition. Good eating and exercise habits greatly affect your body composition. Increasing your level of working out and bettering your eating habits can easily get your body composition to a good level.
If you are flexible, then it means that your muscles are efficient. This means that you are less likely to suffer from injuries. It also means that you will be more likely to ace the first three components of the 5 basic components of physical fitness (remember, they all work together!).
All of these things in turn will help you live a longer, healthier life.