The capacity to be alone is the capacity to love. It may look paradoxical to you,but it is 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.
~Osho

This is the embodiment of why i feel its so important to love yourself. when another loves you and makes you feel good. You're choose to react to it and feel good because of their actions. But if you break it down its still an emotion caused by how you perceived the other. so in essence the "love" you think is coming from another is really a result of your own perception.