I posted a couple of days ago about rewatching season 1. One thing I noticed that was a striking difference in Sawyer. When he told Kate his reason for wanting to get onto Michael's raft, he said that there was nothing worth staying on the island for.
Yet when the time came in season four as the helicopter was about to go down because it was losing power and was too heavy. Sawyer was willing to jump out for Kate. He could've drown, and he was on the island when it disappeared because of his willingness to stay on the island to give his beloved Kate a chance to get away.