I will assume on the island it is warm so I do not need blankets or clothes, and there is running fresh water, and wood so I can fashion tools, like spears to catch fish. I'm thinking for my own mental health what I would bring.

A very large anthology of literature. It would keep me entertained, relaxed, and would give me paper if I really needed it.

An extensive first aid kit. Because everyone gets hurt at some point.

Jeremiah. Because he has lived out in the real world, and can make fires, cook, and can cope. He'd keep me alive. Plus he makes me laugh and I think we'd have fun together.