1.) If you get knocked out people will even use the expression, "He's not there." Your consciousness goes out the window. You eventually wake up though. Death is like this but of course, there's no waking up. This example shows that your CONSCIOUSNESS is PHYSICAL.
2.) When people get hit on the head hard or have strokes, sometimes their inner-voice can change...not so much in the way it sounds in their head but the way in which it functions.
3.) When people do psychedelic drugs such as LSD or shrooms, they have what they call a "religious experience." This shows that a lot of what other people call "religious experiences" might just be some chemicals firing off in their head in abnormal ways.
4.) The eternal soul is SUPPOSED to be exactly that: eternal. Where were you before you were born? Nowhere.
5. When stimulated one EGO part of the brain, religious people thought they were seeing God. Non-religious people thought they were meeting aliens. This is a real science experiment that happened.
Some points that theoretically work:
1.) The soul is eternal but the body and brain are not capable of accessing all of it's memory and/or potential.
2.) That's really all I got. The above is theoretically OK but it just seems too much like wishful thinking.
What now? I die and that's it?
Well, don't get too disturbed. It sucks but it makes you really think about NOW, this moment. You re-evaluate your one shot.
Doesn't this way of thinking make people go crazy and kill people?
I don't think so. In rare cases, maybe. It will probably make you depressed for a little while but not for forever. As for killing people, ...you believe in life being one shot, Why would you fuck up someone else's only shot?
What does it matter if it's all futile?
All of this is open for debate.