REASON # 8: FOR OWN PERSONAL ACHIEVEMENTS!
This reason is related to the previous one in that you do these things because you want to know how much you are capable of doing.
The first time I joined a 10km race, I was really worried about it. I didn't want to finish in the last place and I trained hard for the next three weeks at the gym (yes, I know that the time wasn't enough but to be fair I jogged back then on a regular basis). I would run faster on the treadmill and increased the incline levels.
It was a race for me against all these fit zero-fat runners in short shorts! Running was just for these people back then while the average Joe was still into badminton and basketball.
My goal was to finish and not to finish last, and I got both goals! I was so happy and felt proud of myself. I went back to the gym and forgot about running again till after two years later when Men's Health introduced the Urbanathon Race, which was another new challenge for me and one I set out to conquer.
Then, there's my first Half Marathon Race, first Trail Run, first Full Marathon, new PR's, first Half Marathon Trail Run, first 100km, first 1,000km, etc.
Recently, a new running milestone for me was achieved when I completed 100km in just 7 days so this is an ongoing process.
Run for your own Personal Achievements!