1st - Teach them how to quiet their brain so they can listen easier. Do some mental exercises that will help build that “muscle”to be able to detach from the loud chatter in their brain at times.
2nd - Be extremely rationale, don’t be so quick to pull someone out of their comfort zone when it comes to constructive criticisms about their problems. Talk about their lives step by step and always be understanding to the diversity of problems.
3rd - Surround that person with the associated things they choose to want to chase that will make them happy. Go out of your way to help surround them with these things. Constant exposure to the same things everyday will only help fuel old habits that they're used to doing.
4th -Condition them within these habits to live by everyday, and this is what you'll tell them.
"It will take handwork, perseverance and a lot of will power to get yourself to make this metamorphosis. But just remember one thing, when you make it out of this loop of distress you find yourself in, you’ll be what you’ve always wanted to be. So push yourself and never give up. Fight for you. No matter how hard it gets for you to change your habits, just remember you’re fighting for who you want to be. You have something to fight for. You’re doing what you’re doing for the sacrifice of molding yourself into the person you dream about. Be that person everyday and fight through the fire and the flames of strife. Never back down and fight from ever faltering into depression. Be the change you wish to see in this world, and you sha'll see it."
Caution: Easier said than done. This process is not as black and white as I make it seem. The initiator can only help provide the tools to the person who wants to change, you can't make someone change. If you see promise within them, and that they really want to change though, never give up on them. Fight through the bickering and battles to show them how much you really care about their well-being. One must be very patient within this process though, so always be mindful.