I was told that that average heart is about the size of the owner's fist

So I would grab handfuls of dirt
And grass
And sand

But it would all slip through my fingers, and I was worried that people were the same 

The more I tried to hold on,
The  tighter my grip,
The more I reached out to them 
The more they slipped away

I thought that changed when I met you

I reached out to you, and you didn't slip away 

I could grab your hand, feel your fingers with mine, and you would hold it right back 

When I held your hand, I could almost feel my heart swell as if it doubled its size

But there were other things I held on to,
Not plausible or visible things

Things like the sound of your laugh and the sound of your voice,
Your real smile that came out rarely, which just made it even more beautiful when it appeared 

But you slipped out of my grasp
She took your hand from mine, and she ran with it
And you went with her

What did I do to make you slip away?

How did I let you slip away?