Sad Days

I have good days,
I have rough days,
I have happy days,
I have many sad days.

I cry and I cry,
I remember upsetting things,
I try to look on the bright side,
But I don't remember why.

Why must we have sad days,
I once asked my mom,
She said she doesn't know,

I don't like to cry,
But I don't understand why.