Afterward Jesus findeth him in the temple, and said unto him, Behold, thou art made whole: sin no more, lest a worse thing come unto thee.
Note 8 at Joh 5:14: In saying this, Jesus showed that sin causes the tragedies that come into our lives. Although it isn't always our personal sins that bring these problems (Joh 9:1-3), the sin of someone is always at the root of the problem. (Example: Herod killed the infants [Mt 2:16]. The infants and their parents didn't occasion this by anything that they did. It was the fear that raged in the heart of Herod that caused this mass murder.)
When it is our own personal sins that are involved, these "worse things" come upon us for two reasons. (1) It's the judgment of God upon sin (Le 26:15-16; De 28:61; Ps 66:18, 107:17-18; Isa 13:11, 59:2, 64:7; Ro 2:8, and 6:23), or (2) it is Satan and his forces freed to work in our lives because of sin (Pr 5:22; Joh 8:34, 10:10; Ro 6:16; 2Ti 2:26; 1Pe 5:8; and 2Pe 2:19). Problems, diseases, etc. are never God blessing us (De 28:1-14 contrasted with 28:15-68) or God's method of correction (Joh 15:3 and 2Ti 3:16).
As born-again, New Testament believers, we will not come under this punitive judgment of God (Na 1:2; Ro 5:9; 1Th 1:10, and 5:9). Jesus bore that judgment so we wouldn't have to (Isa 53:4-6, 11; Ro 5:8-10; 1Co 15:3; and Ga 3:13). Therefore, the reason sin is still damaging to us as New Testament believers is that it looses Satan to work in our lives (Ro 6:16).