Just because Usain Bolt can run 100 meters in 9.58 seconds, it doesn’t mean he can run 100 meters in 9.58 seconds all the time.
It’s a lot more meaningful, and impactful, to look at your personal average instead of your personal best. Nobody can perform at their best all the time, that’s what it means to have a personal best.
But everybody can perform better than their personal average at least half of the time, mainly because that’s the definition of average. If you can consistently beat your average, or beat it more than half the time, your average will improve. And that is a lot more impactful than simply breaking your personal best.
The next time you measure your performance, take some time to create a rolling average for your last 10 or 100 or 1000 attempts. It will give you a much clearer sense of how you are improving.