Quicksand.

I was sad today.

I don't know why, I never do.

But I'm just sad, like it hurts to breathe but I know I need to stay alive so I breathe harder. Then, I was breathing so hard that my lungs start to ache. So, I stopped trying.

This feels like quicksand. Yeah, that's exactly how it feels. You struggle to breathe at first, then when it slowly buries you, you stop trying.