Several of Jesus' sayings are difficult, but one that is especially perplexing is "love your enemies." What must have been the thoughts of Jesus' listeners? Love the Romans, the lepers, tax collectors, even Samaritans?
The difficulty is that we can't love just in theory -- to love we must embrace.
But Jesus also says: "Blessed are the poor in spirit, for theirs is the kingdom of heaven." We want to follow Christ, but we're poor in spirit. Only after acknowledging this state and humbling ourselves can the Spirit's power be unleashed.
On our own, we are incapable of doing what Jesus asks of us, but with the Spirit's enabling, we can.