I don't know if it's universally true and it doesn't matter. But I agree with the idea of "if you love someone, set them free; if they love you, they will come back to you". Love cannot be born on the grounds of clinginess or investigation. It seems that a lot of "successful" relationships base their whole core principle on the state of bonding to the point of fusion. Examples can be found everywhere, from the typical everyday interrogatory to joint accounts on social networking, to spying, jealousy. I spoke of jealousy before.
What makes a relationship solid is freedom, not fusion. Yes, a paradox, that's why people can't grasp this concept.
Setting someone free can include waiting, hoping, wondering. It can include a degree of uncertainty that can render one insecure. It is a challenge that you can choose to have or not. But after all this waiting, hoping and wondering, a new level can come: the level of pure security. It's a risk indeed. If the person is free and they come back to you, then you should consider this the most solid ground for your relationship and you can begin the fusion, a fusion that will happen in a totally different manner than in the cases of jealousy breeding committments. You are together by being apart. Nature made you two separate beings for a reason: to build walls, separate, so you can unite. Usually it's the other way around.
The pure security that I spoke of comes from knowing that you didn't put any restriction over the other, that it all came from their own free will. But it's hard, I know.