I don't accept "I know I am" as any form of proof toward any introspective qualities, whether that is sentience or consciousness or even free will. I also don't accept "I just know it" as proof of any deity or higher power, or that there is an objective morality embedded in the universe, etc.

I'll stop responding here, because I think we are just not going to make any progress with each other. Your posit that you can just tell the difference and know it, is fundamentally incompatible with my stance that there must be some method or technique to distinguish what the difference is. I simply do not know that I am the same person today that I was yesterday - I feel that I have good reason to believe that I am, but I also accept that this might simply be an illusion because of the circumstance of having woken up with memories that lead me to that conclusion. I have no way to know that the consciousness that "ended" with sleep last night is really the same one that woke up this morning, outside of the apparent continuity of memory. I find it an interesting and thought-provoking question, but you may also simply decide that you know the answer by feeling.