What is the theme of this poem?

Backwards with Time - The Avett Brothers

Folk always told me that my heart would grow

The older the man, yeah, the stronger the stone

Am I losing my mind?

Am I growing backwards with time?

Some say with age that a purpose comes clear

I see the opposite happening here

Are we losing the fight?

Are we growing backwards with time?

I was young and love was fun

Now it's so serious

Now all the fun has equal pain

There's something wrong with this

For all I know there's more I don't

Oh the little I have learned

For every year of knowledge gained

Is a negative year I've earned

Folk always told me that my heart would grow

The older the man, yeah, the stronger the stone

Am I losing my mind?