What does it mean to love God? One does not love him the way one loves the people one sees and hears and touches, for God is not a person in our sense of the word. He is the Unknown. He is the wholly Other. He is above terms like he and she, person and thing.
When we say an audience fills the hall and a singer's voice fills the hall, we use the same word to refer to two totally distinct realities. When we say we love God with our whole heart and we love our friend with our whole heart, we also use the same words to express two totally distinct realities. The singer's voice does not reall fill the hall. And we cannot really love God in the usual sense of the word.
To love God with one's whole heart means to say a wholehearted Yes to life and all that life brings with it. To accept, without reservations, all that God has ordained for one's life. To have the attitude that Jesus had when he said, "Not my will, but yours be done." To love God with one's whole heart is to make one's own the words made famous by Dag Hammarskjold:
For all that has been, Thanks. To all that shall be, Yes.
This is the kind of thing one can give to God alone. In this he has no rivals. To understand that this is what it means to love God is to see at once that it doesn't come in the way of your loving your friends wholeheartedly, tenderly, passionately.
The singer's voice remains in undisputed possession of the hall, no matter how packed the hall is with people. Those people are no rival to it. The only rival is a person or a thing that causes you to weaken your attitude of Yes and Thanks.