When I ran my first 5k, I struggled to keep up with the other runners. I wound up out of breath and extremely frustrated in the end.
My son (who is also a runner) noticed how defeated I felt even after accomplishing my goal and told me, "Mom, remember that it's your race. You and only you set the pace. When you cross the finish line it's about what you set out to do not how well you did in comparison to somebody else."
I learned a valuable lesson that day about maintaining focus.