One of the ideas my Teacher passed onto me was the idea that fitness cannot be onesided. To really be healthy, and live a life as painfree as possible, there needs to be a balance between aerobic fitness, flexibility, and strength. Many people focus on one, perhaps two, of those components. To really experience health, try adding some "missing" training to your routine!
Aerobic conditioning keeps your heart and circulatory system in top notch condition. It promotes sweating to rid the body of toxins, and elevates levels of endorphins to help you feel good.
Flexibility training helps to elongate your muscles, prevent injuries by allowing greater ranges of motion, strengthens tendon attachments in eccentric contractions, and relaxes the mind/body connection.
Strength training maintains or builds the contractile power of your muscles, keeps muscles balanced in power from left to right and front to back, which plays a large role in injury prevention. Strength training with weights done properly attracts calcium to bones, and is essential to prevent osteoporosis in women.
Also, if you ever get injured (like when I broke my arm), you can at least do one or two of the components (ie, stretch and lift, aerobic conditioning and stretch) while you are recovering. Such a program will speed your recovery as well, bring fresh blood to tissues that need to heal.