It's a bit hard to view the slaps in the face as loving and supportive, but they often are. We dislike whatever disagrees with us, without realizing that they might be acting in our favor.
I see this in myself - I can be incredibly stubborn about some things, regardless of how many times people close to me try to slap me out of it. I guess you're right and, in the end, it's up to the individual.
The slaps in the face are lessons - you may choose to take them or leave them and each choice will somehow impact your life. I think that's where the change starts, when you decide to take the lesson.