One vital aspect of loving and serving other people is that we do not attempt to impose our solutions onto them: instead, we are guided by their preferences and priorities.
Before they become familiar with this way of working, people are often concerned about where it will lead. Various questions arise.
The first thing to note is that you are never actually in control of a relationship. You can control - up to a point - what you do, but you can't control other people.
The bottom line is that you are responsible for what you do; you are not responsible for what other people do. Of course, there are limits to this: what you do can impose constraints on other people, limiting their options; you can sometimes force them to make hard choices when they would rather avoid the issue.
The ethics become less clear when you are not clear about what the other person is capable of doing. For example, is this damaging behaviour a decision they make, a habit they struggle to break or an addiction they are powerless to resist? It is an impossible judgement, but one you have to make anyway if you are to take responsibility for your life and allow other people to take responsibility for theirs.
The point is that you are (very probably) making these judgements all the time as you interact with other people. Most of us don't actually want to control the people around us, even though we get angry and frustrated when they don't do what we want or what we think they should do.
I'm ignoring, for the purpose of this conversation, the times when one person really does try to control other people. The folk who do this are unlikely to be concerned about these issues, and probably don't recognise the dangers of such behaviour - for themselves, as much as for the people they seek to control.
How can you be sure you are helping? You can't.
But, again, that's life. Nothing is certain, as Benjamin Franklin pointed out, except death and taxes.
The fact that you can't be sure what you are doing will actually help, that should prompt you to check what you are doing.
If you are certain you are getting it right, you can - and probably will - keep ploughing on straight ahead. Most of the real damage in peoples' lives is done by the people who are certain they have got it right.
But once you know you don't know for certain, then you have to keep looking, keep asking questions, keep trying to find a better way. Not being certain is what keeps us honest, and keeps us learning.
People sometimes think that if we were to really love our neighbour, we would always put them first and never have any time or care for ourselves. But true love is loving people the way that Jesus taught us, and it is both very simple and very workable: love your neighbour as you love yourself.
You don't impose your solution, but you still participate in helping them to find a way forward.