Re: "There is no heaven or afterlife..."
I admire your debating technique. It's an amazing skill to be able to consciously ignore the massive central point being made about the very definition of one's existance, and then attempt a rebuttal based on some extraneous tidbit. Your point seems to sort-of (not really) work in words, but clearly not in logic. You'll go far in politics. :-)
With the goal of dragging your "thinking" back onto the rails, you may restructure the major point around the following alternate presentation:
Imagine others' observation of you exactly one year before your birth. Etc
Inevitable conclusion: the very existence of your soul in the Universe is very likely finite and symmetric around your physical life. Your pre-conception and post-death existances are almost certainly to be precisely-equivalent voids.
So, enjoy it while it lasts. One day it'll all go black