The hallmark of love is not loving ourselves but loving others and being united to them through love. The hallmark of love is also being loved by others because this is how we are united. Truly, the essence of all love is to be found in union, in the life of love that we call joy, delight, pleasure, sweetness, blessedness, contentment, and happiness.
The essence of love is that what is ours should belong to someone else. Feeling the joy of someone else as joy within ourselves—that is loving. Feeling our joy in others, though, and not theirs in ourselves is not loving. That is loving ourselves, while the former is loving our neighbor. These two kinds of love are exact opposites. True, they both unite us; and it does not seem as though loving what belongs to us, or loving ourselves in the other, is divisive. Yet it is so divisive that to the extent that we love others in this way we later harbor hatred for them. Step by step our union with them dissolves, and the love becomes hatred of corresponding intensity.
from Divine Love and Wisdom, Section 47