"Coulda, woulda, shoulda". How often have you thought that after seeing an opportunity go by that you didn't have a go at. As a friend said to me once, "You miss 100% of the putts you don't try". We are always being encouraged to go beyond your comfort zone, to reach beyond, go longer/harder/further, yada, yada, yada. I'm all for trying your best, and seeing what you can achieve, however...just because you can...doesn't mean that you should.
Just because your car can drive at 150 km/hr...doesn't mean you shoud. Just because you can cross the train crossing when the lights are flashing...doesn't mean you should. Just because you can (or could) streak on the MCG during the Grand Final...doesn't mean you should. Just because you can swim in the Yarra River when it's flowing fast after heavy rain because it would be exciting...doesn't mean you should. Just because you could go out and run a marathon without training...doesn't mean you should. Just because you ran 8 x 400m feeling great...doesn't mean you should do another 2 (or more reps). Just because you ran for 2, 3, 4 or more days in a row for the first time without any problems...doesn't mean that you should try running more days in a row.
Do you get the idea? Sure, you likely could do many of these things, and quite possibly be OK, doesn't mean that there won't be consequences down the line that you might regret. Especially when it comes to running, your body likes consistent routine, that might build on itself over time to extend your fitness. Doing random things that challenge you physically can have great benefits, but you need to consider, and take into account the toll it takes on your body and allow it to recover and adapt before moving on. One pearl of wisdom my old swimming coach passed on was "when things are going well, be conservative".
So in your running training, resist the temptation to...do another rep more than you planned; run (too much) faster than you were meant to; do an extra run more than you would normally; or other changes to your routine. This doesn't mean never try something different, but approach with caution and/or work with a coach to help guide your way.