We all have colorful childhoods, but when we are expected to grow up, the black hole of maturity sucks it up and we leave our childhood behind.
you cannot stop it. no matter how hard you try, you can try to convince yourself you are still a child but you cant bring back your true child hood.
nostalgia is all you have to hold on to.
and i think that's where the term "maturity sucks" comes from.