The speaker looks back at childhood and wonders whether the world has changed or whether they have simply learned to see it differently. What once felt wonderful now seems full of disappointment, fake happiness, and dishonesty. The poem gives small, concrete examples: the way a child trusts the big, fuzzy costumed characters, then later notices how adults talk down to them, or the joy of a chocolate milkshake, which is now tainted by worry about health.
The mood is wistful and a little sad, though also gentle. The speaker asks questions rather than offering answers, such as whether this loss is just part of growing up, and why the world can't stay magical. By the end they accept it with a sigh: "all good things have to end." Still, the final line, hoping the young eyes could have stayed "a little longer," shows how much they miss that simple, trusting view of life.