Why do I say I understand feedback before I really do?

That quick I understand is doing a social job, not a real one. It smooths the moment, closes the slightly uncomfortable silence, lets everyone move on. But you have rushed to shut the door before the thing was actually delivered. You acknowledged the feedback without receiving it, and later you find you cannot really act on what you never fully took in. The urge underneath is usually to end the discomfort of being taught. Sitting in not-yet-understanding feels exposed, so you paper over it with agreement. But that little gap, the pause where you are still working it out, is exactly where real understanding forms. By skipping it, you trade the appearance of getting it for the substance of getting it. Next time, resist the reflex to close the loop. Instead say, let me make sure I actually have this, and then repeat the feedback back in your own words. If you can say it accurately, you understood. If you cannot, you just caught yourself in time. Either way you have replaced the social nod with the real thing.