Wisdom. It all depends on our Wisdom level. And you have the saying, which we give to everybody in the regular retreat, "When in doubt, don't. Consider the task, and ask."
If your Wisdom isn't good enough to distinguish what we can do to help, and what we can't, go and talk to somebody. Find somebody wiser. Go to your good friends. Even if they're not totally wiser, if they're a good, supportive friend, they might see it from a different direction.
It all hinges on how wise you are. It all hinges on much you've worked, in particular, with the reflection on "actions and result of actions", the Law of Kamma. Can you understand what happens when you get angry? Can you understand what happens when you're loving? The more you reflect on actions and their results, the more you're going to understand when you can do something in a situation, and when you can't.
The reflection on "actions and result of actions" is very helpful. Try to figure out, "Well, what's going on here? What was the cause of this problem, What was the result? How could I change the cause? and What would be the change in the result?" You can also try to think of, "Well, how would someone else do it? What would Steve do in this situation? and what might be the result? What would a robber or a thief, or even a murderer, do in this situation?" Just to get a different perspective, sharpen your own wisdom to see what's a beneficial way of doing something, and what's an unbeneficial way of doing something. So, sharpen your wisdom, then hopefully, you may understand when you can do something, and when you can't.