Your brain, which contains everything you know, your entire personality, and all your subjective experiences, will decompose with the rest of your body. The mind and the brain are not two separate things; they are one physical organ in your body, which is proved by the fact that physical damage and physical alteration to the brain changes the way that your mind works. Your thought processes, your emotions, your memory, it's all an extremely complex arrangement of trillions of nerve cells.

If your brain is 10% destroyed, you lose 10% of your mind's ability to do what it does. If your brain is 50% destroyed, you lose 50% of your mind's ability to do what it does. If your brain is 100% destroyed, you lose 100% of your mind's ability to do what it does. There is no reason to suppose that it suddenly and magically regains all its lost abilities and floats off to some other dimension where it will live happily ever after. It's never been observed, there's no known mechanism which could possibly explain how it would work, and the only reason anybody takes the idea seriously is that they (understandably) are scared shitless by the prospect that their existence is going to be temporary, and the prospect that all their dead loved ones really don't exist any more.

Think about it: if somebody has a brain disorder from birth, and they grow up mentally retarded, are they still retarded in the afterlife, even though there's no physical brain to have a problem with? Or do they suddenly develop the intelligence and personality of a non-retarded person, thus becoming, essentially, a completely different person? The brain is the mind, and the mind is the brain. The death of the brain is the death of the mind.