I’m glad you’re having a good time of things.

I think if you’re interested in determining the difference, probably the thing to do is identify the limiting variable normally and compare it to how you felt after running further this time. For instance (and I’m not saying you did this, it’s just an obvious example), someone can run a given distance while being careless about proper breathing and feel like they are dying at the end, or focus on breathing the whole time and then feel basically fine while running the same distance even a little faster. Same with changing gait, eating something more appropriate at a more appropriate time beforehand, being more appropriately hydrated, doing a better job stretching beforehand, pacing yourself better at the start of the run, etc. There are also external variables like heat and humidity.

There are periods of time where I did a lot of running, but I’m not really an expert on the subject, so I’m just spitballing from personal experience and there will surely be other people who know more about this and can give more actionable advice.