> When you're younger, those models are less complete and larger parts of your waking moments are needed to build the foundations of these models, so you feel l

> When you're younger, those models are less complete and larger parts of your waking moments are needed to build the foundations of these models, so you feel like time is slower since so much more of your time is kept "fresh". As a corollary, if you want to keep on feeling young and feeling time pass slowly, you need to keep on incorporating "new" experiences into your life that extend (or change) your mental models.