Anyway, there are about five things that can bother you running.
Your feet or legs can hurt.
You can be tired, out of breath.
... hot, thirsty or dehydrated.
I just was in the gym and I did a five k around the track. It is going to be 95 today so I didn't want to run outside. I wasn't particularly winded, or bored, since I had music. I was hot, but not excessively so. My legs hurt at first but I stopped noticing that after a few times around. I was motivated enough to complete the run, setting a personal record of 30:57. The trick was to run as slowly as I could the first part, run comfortably the second mile, and then have enough energy left to speed up for the end. Basically, I wanted to average 11 minute miles, but I ended up running a steady pace of about 6mph most of the time, giving me 10 minute miles. I think I could easily improve my time to 30 minutes, and from there a few minutes less. I was only aiming for 35 minutes today and I far surpassed that. I think the trick is going to be running outside (once it is cooler).
I think this is really a metaphor for how I approach virtually everything in life. Analytically, obsessively. The list of five things that can bother you running allows me to see what my main obstacles are. For another goal or activity, it will be something different. I've discovered, for example, that my limit in the five k has nothing to do with aerobic endurance, for now. I could have run faster if I were not as hot. It has a little to do with my legs. It is not a limit in speed, per se, since I ran quite slowly. So what I have to do is come closer to my limit in endurance, running a 5k in which I am actually winded at the end. I also need to run a mile faster. My record is 9:20, which should be easy to beat since I just ran slightly over 3 miles in 31 minutes.
Here's how I think of it: I can walk 5k in 45 minutes, at a brisk pace. The world's record is 12 something. Best amateur times in my town are around 17 or 18. My 20-year old daughter can do it in 24, without being a serious runner at all. I suspect I'll end up at about that, and I will be quite happy. I have no interest in 10k or longer at the moment, though you never know.