Compassion to friends: stepping in vs. letting them learn on their own

There is a story about how the Buddha will knock on your door if your house is on fire, but he will not kick it down because you have to answer the door yourself. This is analogous to the Four Noble Truths, in which one must realize their suffering, and from that they can make the effort to find the path to the cessation of suffering. The Buddha will not force you down that path, nor will he be your savior; he will only help you if you ask him. However, the Buddha also asks those to practice sincere compassion for others. My question is: if I see a friend suffering (let's say from a slight alcohol abuse or they think that they are ugly), yet I think they will never understand their suffering, how can I give my compassion to that being that needs help to deal with their suffering, when their understanding of suffering must come from within? They need to come to the realization of their suffering, but I know that these people will never see the light themselves. Where's the balance in this tricky situation? These friends are unwilling to change their unhealthy habits, but I, as one who tries hard to practice compassion, find it hard to just let it slide and hope someday they will realize their suffering and understand that it exists, and that there's a path to the cessation of it. Any insight would be much appreciated. And I hope my thoughts make sense to some of you.