With coke, your tolerance gets built up real fast. So you won't feel the same high as you did before with the same amount. Also, the more you take it, the worse you feel when you come down. At first, when you take it, when it wears off, you just go back to feeling normal. But each time you take it, as you come down, you feel a little bit more depressed each time. Over time, as your tolerance builds up, the high isn't as intense and doesn't last nearly as long as it once did, and when you come down you are shit-in-the-fucking-dumps depressed. At this point, you need way more than you did when you first started just to get the same feeling, and when you come down into depression, you KNOW that the only thing that will make you feel better, and make you come out of it is more coke.
Pretty soon, you will only have two realities, high and feeling good, and not high and depressed.
but you won't wreck a car on it like alcohol