Of the five theories in this article in the Comment is Free section of the Guardian I think the most accurate is by Catherine Wybourne a Benedictine nun. Maybe not the loving God above all things but the rest rings true.
"Love is more easily experienced than defined. As a theological virtue, by which we love God above all things and our neighbours as ourselves for his sake, it seems remote until we encounter it enfleshed, so to say, in the life of another – in acts of kindness, generosity and self-sacrifice. Love's the one thing that can never hurt anyone, although it may cost dearly. The paradox of love is that it is supremely free yet attaches us with bonds stronger than death. It cannot be bought or sold; there is nothing it cannot face; love is life's greatest blessing."