Need help with this poem riddle.

Hi guys, the poem riddle below is meant to help a treasure hunt game, called hunt the mouse, which is to find a gold coin with a mouse logo on it. Does anyone know what it means?

"You went by so fast,

I may not be the last.

As your shadow casts,

there can be contrast.

When you preserve your past,

I may be flabbergasted.

So as you pass,

I wish you have a blast."