Diet. Exercise. Follow your dreams?

It's no secret that good physical health -- what you eat, if you do cardio exercise and lift weights, or if you have proper sleep patterns -- is the key to a long life.

But as far-fetched as they may be, your dreams may be the real factor in how long you live. Here are a few reasons why:

Happiness and health.

According to a study published by the Journal of Proceedings of the National Academy of Science, there is a direct link between mortality rates and people's moods. The study says that there is evidence that surviving longer and having a reduced risk of disease is associated with "positive affective states" and "other measures of well-being."

Similarly, being unhappy can negatively affect any existing medical issues as well. Dr. Dilip Jeste, from the University of California, San Diego, notes "heart disease can cause greater stress in some people than in others, which might affect their level of enjoyment."

Translation? It's a vicious cycle -- being in poor health can cause unhappiness, and this same unhappiness can cause poor health. But you can avoid these health issues by being happy through the achievement of dreams.

A journey, not a destination.

Naturally, dreams aren't always realized. For all the amount of faith and willpower you may have, sometimes your dreams don't turn out exactly the way you envisioned. However, success is a journey, not a destination. Merely chasing after the goal can be enough to increase your sense of fulfillment and levels of happiness and health.

Enjoy yourself.

You know the saying -- "choose a job you love, and you will never have to work a day in your life." Support yourself, but still work towards what you hope to do in the long-run, whether through hobbies, classes, or an entirely new job itself.

When we ignore our hopes and dreams, we not only avoid getting the most out of life, but we avoid the chance at happiness and a long life. Shoot for the moon -- even if you don't get there, you'll find yourself in good health regardless.