If you want someone to listen to you, even for their own good, you should be in a position of POWER over them or you should be their MOST VALUABLE person at that time.
Not second or third most valuable, only being the first will do the trick. It does not matter what they are to you (important, invaluable, love of your life, your primary responsibility..), only thing that matters is what you are to them. If we are not that significant to them all we can do is be on the sidelines hoping nothing goes wrong and be ready to pick up the pieces when they are breaking apart, without giving up.
