Lots of research has demonstrated that most crack addicts (and alcohol addicts, and nicotine addicts) who try to quit relapse. I thought that was an accepted part of science. Why do you think it sounds kinda off?
It's off because something that is impossible denotes some sort of 'law of nature' that cannot be avoided, where as in reality it's more brain/willpower related.
yes "impossible" denotes some sort of 'law of nature' that cannot be avoided, and "almost impossible" doesn't.