The reason our childhood years seemed to pass so much more slowly than our adulthood is that they were filled with novelty and excitement, memorable first experiences: learning to ride a bike, entering a new school, making new friends.
Events, experiences, things are memorable not by some inherent quality, but rather become memorable by virtue of being different from our everyday life. What matters is the magnitude, not the sign: both the best and the worst times in your life will stick out in your memory.
Memorable experiences come in all sizes: cooking a new dish, meeting up ...