Jealousy in a relationship, is it unhealthy?

Is it wrong to get jealous when some one else is moving close with our partner? People say that those who are not secure of themselves/confident of themselves get jealous. Do you agree with that? There are situations when you can't help getting jealous. Suppose if you don't get jealous at all, does it mean you don't care for the relationship enough? I think every one has his/her own limit and if some one crosses that limit he/she will definitely get jealous. A man may be loving truly his partner. At the same time if some very attractive female gets close to him, he may stumble and lose his morality. So there is nothing wrong in his woman getting jealous on the other woman in his life. If you say it is narrow mindedness to suspect your man, then you may lose him fully at one stage.