The good news we are to preach is that God loves and wants us to know Him as well as He knows us. The Gospel is a message of reconciliation and restoration. It transforms lives. What an exciting thing to be a part of--but not everyone will receive that message. This is a world that contains evil. That was/is not to be a disciples' concern.
The second part of the command, 'Heal the sick' makes many of us uncomfortable. But it is clearly said. Did you know that a huge percentage of physical illness have a direct relationship to emotional (spiritual) problems? We cannot 'order' healing--bodies die and evil exists. But it was a lack of faith that hindered the miracles of Christ Himself. Perhaps we, like the disciples, need to ask Him to increase our faith and leave the results up to Him. But the bottom line is: we need to go! Religion makes us comfortable. Faith in Christ is not such a settled thing. It will call us out of our comfort zone and take us into places we may find uncomfortable. It will change lives--beginning with our own!