Man, nothing shuts up your mind like your body. You can be worrying about twenty different things, worrying if you even should be worrying and then worrying about that... but put enough sensation into your nerves and you'll be thinking about exactly one thing.
It works for good and ill. The whole "be here now" thing is great if your worries are excessive, but if you have shit you actually gotta take care of you might need to be there then. I've used sex and pain and exertion to forget my cares, and I've used them to forget my obligations.
It's just such an experience though, to be changed from a constantly thinking and processing creature into an absolutely primal one. When there's a cock in me and things are right, there is nothing else. At all. I am an island in time and space, alone with my pleasure everywhere and forever.
There's a lot of paths to that state. Drugs, absolutely. Meditation, if you're good at it, but I'm terrible. Being just ridiculously sleepy. Exercising to the absolute top of your capacity. Pain, if you can accept it. Music, if you're really really into it. Sometimes nothing in particular at all but just the feeling of a moment. But for me sex works better than anything. It's a free, safe, guaranteed return ticket out of reality.
Man, and we giggle when we talk about sex. I think we're just afraid of a power that awesome. That and the sheer absurdity that such a transformative experience involves gooey body fluids and silly noises.