It may look paradoxical to you, but it's not.
It is an existential truth: only those people who 
are capable of being alone are capable of love, of
sharing, of going into the deepest core of another
person -- without possessing the other, without
becoming dependent on the other, without 
reducing the other to a thing, and without
becoming addicted to the other. 

They allow the other absolute freedom, because 
they know that if the other leaves, they will be as
happy as they are now. Their happiness cannot be
taken by the other, because it is not given by the other.

                                                              -- Anonymous