Actually, I think you have to know that whatever advice you give, they may not take it. The priority should be on keeping the friendship rather than giving the best advice. Your best advice is usually, 'Walk away from him! Tell him you never want to see him again!' But if you are dealing with someone still in love, nothing you say can change their feelings. All you can do is be there for them and pick them up every time they get hurt. Until, that is, they are ready to move on for themselves.