Treadmills kick my butt

So I decided recently that I really should establish some sort of physical goal in my life, since I've never ever done that before in my life and with the encouragement of several friends Nic & I have decided to run a 5K. So in my head the thought of running a 5K sounds so fun and exhilarating but I'm learning the training part of it isn't so pretty. Take for instance tonight when running 14 out of 30 minutes on the treadmill made me feel as if I was about to lose my dinner. Yet somehow in the end I always manage to feel better about myself despite the nauseating feeling I felt only moments before. Why is that? Nic & I were talking on the way back about setting physical goals and health goals and suddenly I realized that's why all the pain melted away in a matter of seconds. We are designed to have a purpose/goal for our lives, and as small a goal as running a 5K may seem it makes me realize the importance of the bigger picture. I am worth something and I am put here for some purpose.