The Last Man (SF movie trailer).

Tov Matheson is a war veteran with PTSD (post traumatic stress disorder) who perceives that the end of the world is coming.

After establishing a relationship with a dubious Messiah, he leaves his normal life and begins the construction of a shelter underground, training himself, in an extreme way, at the cost of losing everything and making people believe he is insane.

When he also believes it, something extraordinary happens.