A personal record (PR) is special to any runner. By definition, it represents the fastest time a runner has ever covered a given distance. It's also possible, or even probable, that it represents the fastest time they will ever cover that given distance.
I've been working on my 5k time for close to a decade. For me to set a new 5k PR takes at least five months of dedicated training, a conscious diet, and very careful planning about how to approach the week leading up to the race. There have been times when I trained for months and was not able to break my PR. The 5k time that I posted as a 32-year-old held tough for three years before I was able to break it.
With all that work and dedication to a goal, I assume that I'll be overly excited each time I break my PR. On the contrary, I often feel nothing. In fact, I consciously remind myself that I accomplished something special, and to be proud. The reason is that setting a new PR is a sign of consistency and hard work leading up to the race, not during.
Though it takes a very strong effort the day of the race, it's quite possible that I've had better efforts leading up to the race. Some of my best efforts end with mediocre times. There are days when I'm not feeling well but still get myself outside to train. Those days can take a heroic effort and result in a forgettable time.
A PR is a sign of consistency, and well-planned training, it's not a sign of pure effort on a given day. I can't will myself to a new PR without putting in the work. I just run at the same level of effort as I have on dozens of occasions leading up to the event, but each mile split is just a little faster. That is the magic! I can perform better than ever by putting forth the same level of effort, as long as I've put in the hard work.
So, when I finish a run and look down at my watch to see a new PR, I'm proud of the accomplishment, but more importantly, I'm proud of all of the hard work in the months leading up to the race. It feels like any other training run, but it is the payoff of many hours of hard work. It is something to be proud of.