One of the hardest lessons to learn, is to let others have their own journey, no matter how wrong you think they are.
As parents, this can be like walking a tightrope between disciplining and letting your child "experience" the world of hard knocks. This is where your parenting intuition comes into play.
However, for the grown people in our lives who we know are doing the wrong thing, even when they come to us for advice, and don't take it...allow them their journey.
It's natural to want to control not only our lives, but those around us...whether they are our kids, significant other, family, friends, or co-workers.