In Deuteronomy 6:5, the sense we are left with is this: It is with our very selves that we are to love God. All that we have at our disposal: our power, our emotional health, our relational influence, our physical strength - all of it - our VERY SELVES - can be oriented in love toward God and toward our neighbor.
Opportunities to love God and others with our strength come around everyday, but we are not always ready to be faithful when they do. We are not ready, because we too often waste our strength on selfish things instead of on loving God and our neighbor in these ways. Believe me, I know.