According to some people, one of the worst things that a person can be is an obsessive. In fact there are many tasks that require obsessive focus, and being of an obsessive temperament can be an advantage in a number of pursuits.
If you are a researcher, being obsessive helps. If you are a priest or a teacher, being passionate helps. Some fields very much require obsessive approach; and the people who think that people with such temperaments are necessarily bad are wrong.
Now there are any number of people who do not want obsessive attention directed at them. That is fine; it can be directed at other things. The people with such temperaments should be steered toward pursuits that require obsessive focus. And of these there are many.
If someone can feel passionate about a person to the point of being obsessive about them, then he can do the same thing in other pursuits. He can become equally focused on God, or on a cause, or on a research project. There are many in psychology who think that such people are incurably sick; but all that this means is that they have no idea how to deal with them. Basically they do not know what they are doing. They do not know how to help such people. It does not mean that nobody can.
The solution with the obsessive types is to direct their obsessive attention toward pursuits that are viable. Direct them at God. Direct them at causes. Direct them at projects that require obsessive focus. Give them something to focus upon that they can feel passionately about and pursue relentlessly. The result will not only be these people doing something productive rather than annoying. It will be the world benefiting vastly from what they have to give.