The Island is a metaphor of ones lowest point in life where nobody else can really save you but yourself. Mine was depression and alcoholism. I was miserable at that point, and at the same time I kinda taught drinking helped me cope for a while. At some point you find comfort in your misery. Which is why deciding to take the needed steps to get out of it is not as easy as it looks. When you try to step out of it, there are many hurdles that will just make you want to go back and stay in that Island. But I did manage to find the strength to get out of it and eventually help myself.
We all cried when he lost Wilson but this scene has a greater meaning. He left part of himself on that island, his view on it says that. His life wasn't same ever again, he became a different person. Island was his curse but at the same time his safe place from certain death. When he looked on island, I think that only at that point he understood how much that island helped him survive and struggling alone. We can also tell that he fled from himself in this scene.
1:58 he left old himself there, all his pain and life. This is the hardest scene for us introvert persons. You saw all your pain back there. You want hardly to go from there but you couldn't simply hate that place, because it was only your safeplace in one moment of life. That island destroyed him and saved him at once. What doesn't destroys the man, it makes him much stronger and that's my opinion on this scene.
I kind of like the way the music comes in as he floats away from the island as much as he hated being there it was keeping him alive and it was his home in a way it's kind of hard to say goodbye