Remember, now that you have been made well, give up your sins or something worse may overtake you. What Jesus says to the man he had healed may sound rather odd to our ears. Is Jesus associating the man's former condition with the man's sinfulness? Is Jesus implying that the man’s illness resulted from his sins? If that be the case, isn't Jesus contradicting himself? (When later on he will be asked whether the blind man healed by him was blind on account of his sins or his parents' sins, he will reply in the negative [cf. John 9:2ff]). It would be safe to assume that Jesus is not contradicting himself here. Jesus is merely stating a fact: that we are all prone to sin (cf. Romans 3:23). Moreover, Jesus is aware that when pressed to a corner by sickness, even the strongest human person can break (think of Job in the Old Testament). This man has been paralyzed all his life. He has had to depend on others for his livelihood. As a Jew, it was highly likely that he heard people talking about sickness and poverty as consequences of sin or as indications that God had withheld his favor from a person. Handicapped and unable to participate even in the most ordinary of human activities, he might have bought into the idea that God had withheld his favor/blessings from him. With no one to plunge him into the pool whenever the waters are disturbed, a wave of desperation might have overtaken him. And as he lay there beside the pool day after day staring into nothingness, one can only imagine the thoughts that were playing in his mind. Circumstances might have led him to buy into the popular belief of doubting God's existence and love for him.
Jesus did sympathize with the man and gave him back his life. He too knew that the glory of God is a human person fully alive, and that this man's condition might have become an impediment to that. However, Jesus reminds him that as unfortunate as his condition was, it was not the worst! He was physically handicapped, but he still had faith (otherwise he would not have been at the pool side). The worst that can happen to a person is being separated from God. For without God in one's life, life loses meaning since there remains nothing to live for. Separation from God takes place when one persists in sin. The healed man had to be careful not to fall in sin even as he reveled in his newfound fullness of life.