Random Riddle: Laughter and Tears

At one point I had it,
But now I can’t find it
So I must buy it.

It’s a challenge to make
But tempting to take
So often I do.

Adversity strikes,
I surely am in it,
Seldom on it.

Laughter and tears
Are all but forgotten
When they’re given it.

If you ask me for it
I will share it with you
Always, openly.

I struggle to quell
The impulse to kill it
Though it will surely kill me.