Why does everyone secretly harbor regrets about the past?

When I was 8 years old,
just playing King of Fighters with my cousin would make me happy.
Even hearing the news that I was going to my cousin's house would make me excited and eager, imagining playing co-op mini-games with him.
At 16,
secretly spending 90 yuan to buy a half-price legendary skin in Honor of Kings would make my blood race.
It was like the agents on Mission: Impossible and The Matrix—thrilling, dangerous, and full of fun.
Using a Redmi phone, playing at 30 frames per second, proudly showing off my skin to friends, savoring the silky feel of the skin during evening self-study sessions for an entire month.
Time has passed,
if I could go back from 16 to 8 years old,
I definitely wouldn’t feel so excited and happy about watching my cousin play King of Fighters; I would just feel bored and dull.
If I could go back from now to 15,
I also wouldn’t feel so tense and excited about secretly spending 90 yuan to buy a half-price skin, because I don’t care anymore.
So,
if there’s something you believe will make you happy,
something that excites, brings joy, and gives you a sense of fulfillment,
just go ahead and do it.
Because you never know if the next moment, you might suddenly lose all interest in that thing,
and the world will have one less thing to make you smile.
Time waits for no one.