You may be doing the wrong type of exercise, according to The 8 Colors of Fitness ($20.99). The author, Suzanne Brue, believes that your personality affects how you think and feel about exercise. So if you know your likes and dislikes, you'll be able to choose sports or types of workouts that are right for who you are. If you enjoy it and it jives with your personality, then you'll be more likely to stick with it.
In the book, you take a Myers-Briggs personality quiz to figure out which color of fitness you are. You can also take it online. It may help you realize that if you prefer alone time, then running in the woods might be better for you than a step aerobics class. On the other hand, if you're a people person, you may enjoy joining a soccer team instead of working out solo at a gym.
If you're curious to know what each color means, then
When it comes to fitness or being physical:
Reds are quick responders
Whites like to plan ahead and are visionary; they prefer calm spaces and don't like to be rushed
Greens are outdoorsy types and nature lovers
Golds are traditional and conservative
Saffrons are playful and value individual expression
Blues like to create their own safe space at a gym
Purples like routine
Silvers enjoy exercise that's disguised as fun or a way to meet others
This book gives great insight into why certain types of fitness are more appropriate for your personality. It's amazing no one has thought of this sooner, but it makes so much sense, doesn't it? If you're interested in learning more, you can order this book through Amazon.