When we were children, we always had many unforgettable memories as if it had just happened yesterday. But as time passed, these memories seemed to fade or even disappear without a trace. Why is that?
First of all, as we grow up, so does the brain. As children, our brains are in the developing stage, with abundant neuronal connections and relatively strong memory. But as we age, the brain matures, neuronal connections decrease, and memory weakens. Second, as we grow, so do our cognitions and emotions. Childhood memories are often associated with simple emotions such as happiness, fear, anger, etc. But as we age, our cognitions and emotions become more complex, and our memories of the past become less profound.
In addition, the loss of memory is also related to the forgetting mechanism of memory. Forgetting is a natural process of the memory system that helps us filter out unimportant information and retain important memories. As we get older, we are exposed to more and more information, and the forgetting mechanism works more frequently, causing some memories to be forgotten gradually.
As we grow, so does our state of mind. Childhood memories are often associated with a carefree, free-spirited state of life. But as we age, we face more stress and challenges, and our memories of the past become less focused and valued. 
In conclusion, growing up without childhood memories is a complex issue that involves multiple factors. Although we can't go back in time, we can cherish every moment of the present and experience and feel every moment of life with our hearts.