To What Extent Does Free Will Exist?

The post that was quoted here has been removed

It is like, but maybe different, a man who first chooses to use heroin. But after experiencing it a couple of times is now hooked. It is a mind altering drug. Not only the high, of course, but the craving is so great, to stop is nearly impossible.

He goes from having the free will to do it, to being basically lost in it.