Cutting is just like a hot shower. At first, you don't even want to get a shower. But when you're in it, you don't want to go out. Cutting has a lot of resemblance to that. You never picture yourself as a cutter until you start, and then it's too late. Then it's too hard to stop.
When you first get in the shower, it's hot and burns a little - but the water feels good. After a few seconds, it doesn't burn anymore, so you turn up the hot water until you can tell, that it has gotten hot again. You continue until you run out of hot water. Then you step out and look down on you bright, red body. You didn't notice how hot it was because your body had built up a tolerance to it. But the entire time you were in the shower, letting the scalding water cover your whole body, it was burning hot. And you didn't even realize.
That's how cutting is. In the beginning, it hurts a little, but the good feeling it gives you overpowers the pain. So you continue. Eventually, your body develops a tolerance, and you are forced to cut deeper to feel the same pain as in the beginning. You keep making the water hotter, and you can't even tell how much it's burning. Until you finally step out of the shower.
You look down and realize what the blade has done to you. You realize that you have to stop, but you don't. Just like you don't stop taking hot showers.
That is cutting.