FEAR

"There is nothing to Fear but Fear itself." --FDR

That Roosevelt quote was from a time of war. We were told by secondary characters that the Island, and therefore everyone attached to it, was also in the midst of a war.

The conflict was murky.

First, it was the survivors against the inhabitants, the Others.

Second, it was the survivors against their fellow survivors.

Third, it was Widmore against the Others.

Fourth, it was everyone against everyone else.

Fifth, it was Jacob against his brother.

Finally, it was Jack and Kate against Flocke.

If you are in the school of thought that LOST was merely a character study of individuals, then the show could be considered as thesis on how they coped with their personal fears.

Fear is an unpleasant emotion caused by the belief that someone or something is dangerous, likely to cause pain, or a threat; a mixed feeling of dread and reverence; a feeling of anxiety concerning the outcome of something or the safety and well-being of someone; or  the likelihood of something unwelcome happening.

What were the main characters biggest fears?

Jack's biggest fear was failure. He always had the drive to "fix" people, even though people who could not be cured by his medical skills. Part of this fear was based upon his relationship with his father; he feared that his father would not acknowledge him as an equal.

Kate's biggest fear was responsibility. She always ran away from her mistakes. She always tried to avoid the consequences of her actions. It may stem from the fact that she does not believe in commitment because she came from a broken home.

Locke's biggest fear was acceptance. His loneliness was compounded by the fact he had a crazy mother and he was shuffled from foster home to foster home. He never fit into the social situations. He wanted to be someone else in order to belong to a group, but throughout his life people rejected him.

Claire's biggest fear was motherhood. She was a rebellious child who did not get along with her family. She wanted bigger things for herself. But when she got pregnant and her boyfriend ditched her, she could not handle raising a child on her own. When she gave the baby up for adoption, she was riddled with guilt.

Sawyer's biggest fear was acceptance. His entire life was spent tracking down his parent's killer, which turned him into a person that he himself could not like or stand. He took it upon himself never to get close to anyone so he would be an anti-conformist. He thought that if he was accepted by other people his goal in life, revenge, would be thwarted.

Hurley's biggest fear was rejection. He had a difficult time dealing with people on a personal level. It was very difficult for him to ask women out on dates. It may be basis on the fact that his father left him as a child. As a result of this void, he consumed food instead of seeking love.

Jin's biggest fear was poverty. He was the son of a poor fisherman. He thought the only path to happiness would be wealth. When he lucked out at met a rich heiress in Sun, he thought that his life would be exactly what he wanted it to be: easy and rewarding. But Sun's father did not respect him. Jin turned into a criminal enforcer making him a poorer man than he ever was before his marriage.

Sayid's biggest fear was accountability. He knew what he did in his past like torture was morally wrong. He was brought up in strict religious beliefs, but his actions were constantly at odds with those beliefs. When he had to make a decision, he continually fell back on his military behavior over a moral choice. He chose to work for the U.S. military in Iraq to avoid the accountability for his treason. He chose to work for the CIA to betray his friend in Australia instead of being accountable for his own past crimes. He chose to become to a secret assassin for Ben in order to be remain above authority. He knew he had turned into a monster but he did nothing to change himself.

The character study question would be whether these characters ever overcame their fears to find eternal happiness. Did Jack overcome his fear of failure to lead the plane survivors to rescue? Based upon the body count and only a handful of people to actually depart the island, no. From a personal level, did Jack's death after fighting Flocke a success? No, not really because living would have been preferable end than dying.

Did Kate get responsible in the sideways church by allegedly committing herself to Jack? We don't know because we saw that relationship start and blow apart in the O6 arc.  Did Claire overcome her fear of motherhood and take care of Aaron? We don't know that, probably not, since she had to "re-birth" Aaron after death in order to smile. Did Sawyer find acceptance by other people for who he truly was? Perhaps, with Juliet in the time skip and the reunion with her in the hospital. Did Hurley find love in the end? With Libby, there was that probability even though their relationship was clouded by the fact they were both at the mental institution but did not recognize each on the island is a troubling mystery. Did Jin overcome his fear of poverty to find a materially rewarding relationship with Sun? In life, they never came so close as they did in death. Did Sayid ever overcome his accountability worries? He did not have to because he was never punished for his actions.

Which brings up another point. The fantasy ending that the main characters "got" want they truly wanted from the island "time" did not change, redeem or improve any of the main characters personality flaws. There was no great revelation that changed their hearts or minds. At best, they survived their fears at a basic level but at most times those fears were repressed by the physical danger present in their daily island time.