I am pretty damn sure. Your brain, everything that makes you you, is a biological computer (for lack of a better word) of which we have an extremely comprehensive understanding of how it functions and the processes, both biological and psychological, that form a personality. There is no magic sauce or spirit that leaks out into the void when you die. It is your biological circuits ceasing to function and decaying.
I say this as someone who believed in an afterlife well into my late 20’s. It is a belief we tell ourselves to cope with the reality of our own mortality. We will die and there will be nothing, so we tell ourselves that maybe there will be something because it makes the pain easier to handle.
It is not wrong nor necessarily bad to constantly question things and to desire to look deeper into information presented to you
But continued denial of something that is extremely well understood, studied, tested, and researched isn’t healthy skepticism - it’s wilful ignorance for the sake of soothing one’s fears.
The human brain (the brains of most creatures, really) is now better understood than it ever has been and new technology is making studying it easier and faster than ever before. At no point, past or present, has there ever been even a tiny minuscule sliver of anything even remotely similar to a soul or afterlife being detected or observed. What we have observed, however, are the parts of a brain that are responsible for emotions, memory, personality, logic, reasoning, etc dying and ceasing to function.
The brain is an extremely awesome and complex thing but it is not powered by magic. I am trying my best to not mean any disrespect here - like I said I believed in an afterlife well into my 20’s - but the entire premise of an afterlife is basically magic. It’s fantasy. It makes the crushing pain of our own death easier to deal with.