Running is a very mental game. You start running and right away we often want to stop. Here are a couple tricks to make sure you don't fall victim to the jerky voice in the back of your head telling you to stop.
1. Decide before you start how far you are going.
2. When you feel like you want to stop, increase your speed. This can actually give you an energy boost and cause you to catch your second wind.
3. Set time goals to keep you motivated. Running the same distance and the same speed every time you run gets very monotonous. Change it up to keep it interesting. It's a lot more fun.
Just because you have never been a "runner" does not mean you can't be or aren't one. We can all be runners.
I have always considered myself a "swimmer". When I won a small 5k a few months back I was talking to a few of the other women who ran with us. They were congratulating me and telling me I was a great runner. I told them I'm not really a runner. They were marathoners and ultra-marathoners and when I told them I wasn't a runner they told me it was time to rethink what I was saying.
So I thought about it. What makes someone a runner? Well, I suppose it's if they run. You don't have to be winning races to be a runner. Once I realized that, I was a little less intimidated to commit to running and be in running races.
All the ways you have defined yourself in the past are out the window. You can be whatever you want and if being a runner is one of those things then take it!