It's simple really: I run because I really like food and alcohol. Running is my way of detoxification and keeping excess fat off my body. Well, that's the half of it. The other half is I take pride in being a recreational athlete, chasing fitness targets, developing mental resilience and molding my body into something that's visually pleasing.
With that said, every other motivation and benefit obtained from running doesn't hold a candle to the advancements made in mental resilience through running. Fitness and physical appearance are pretty standard motives but it's deeper than that if you dig a little. No other sport tests your perseverance and determination like running. When you run and things get hard there's that little voice in your head that plays tricks on you. It tells you to slow down, to quit, that it hurts and why bother with the pain and burning sensations; no one should volunteer to suffer. However, If you can overcome the desire to quit, the urge to stop, and find the determination to finish what you've started I guarantee that you can and will overcome any other obstacle in life. You won't quit. You won't slow down. Until you get what you want. That's what running can do. That's why I run...so I can finish strong in life.
Anyway, I really feel good about myself when I run...especially when I don't feel like it but get it done regardless, I'm sure you do too. There's a feeling of accomplishment there. Take it. And later you can reward yourself with a slice of pizza...or two..and a beer..or more.
Run. Eat. Drink. Repeat.