If so - on what basis are you sure that death is total extinction?
We all agree that the body dies - but you apparently believe that the 'soul' also dies (or believe that there is no such thing as a soul in the first place) - You believe that after death there is absolutely no trace of anything of you left at all.
Total and irreversible extinction of the whole self is what you apparently are 100% certain about.
Against your certainty is almost-every human that has ever lived in history and throughout the modern world.
Against your certainty is that there is zero evidence of the utter extinction of everything - you don't I presume, imagine that 'science' has 'discovered' that there is no soul?
(It could accurately be said that science has not found any detectable soul, but that is irrelevant! You are claiming 100% knowledge! Science hadn't detected the Higgs boson until a couple of years ago - did that non-detection prove with 100 certainty that the Higgs boson did not exist? Of course not! The existence and survival of the soul is a subject on which science is silent. Indeed, insofar as 'science' is built on the assumption and practice of excluding any 'religious' explanation - then it is a subject on which science will always and necessarily be silent.)
You apparently are 100% sure (in the teeth of the opposite consensus of mankind and zero evidence) that non-existence of the soul and/or non-survival of the soul after death is the default belief, and that belief in the survival of the soul is explainable as... what?
But most people in history that believed in the survival of the soul after death (and many alive today) regarded the post-mortem soul as existing in a miserable, horrible state - forever!
They believed in the soul living-on after death of the body as a demented spirit, or ghost, or in some hellish torment or terror, or bound to an endless cycles of reincarnations (mostly horrible, punishing, degrading).
Was that wishful thinking?
No; the true default belief is that the soul survives death - and to believe with 100% certainty that death of the body also means utter destruction and annihilation of the soul is an extraordinary assumption!
How can you be so sure about this?
And if - on serious reflection - you are not 100% sure; then you have some serious thinking and investigating to do; because if you are wrong about this (if you are pretending to be 100% sure without any good reason) then you may be lying to yourself (wishful thinking, perhaps?) and deliberately pretending to a false and unjustifiable certainty about something you cannot possibly be certain about.
And if you are completely wrong, presumably there will be consequences of some sort, and it is possible that these consequences (whatever they are) may last for eternity.