Spoilers: Please help me understand the ending

The parts where Cole and Maya's relationship were explored in the past all really happened. The parts that followed after the supposed apocalypse were actually Cole's brain dying and creating hallucinations as he lay dying of the gunshot wound.

The events surrounding them as they fight for survival are all about his fears of not being able to support his family as they constantly run from one place to the next where is no food and barely any supplies.

It would need a good couple of watches to catch all the symbolism. I was playing Elder Scrolls Onine while watching so I didn't catch everything. Part of me even suspected that was what was happening and that nothing was real (the lack of aliens or of impending spaceships, etc).

It's all very psychological.

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We've become a race of peeping toms.

Stay with me here- there was no astroid crash, aliens, or any of it. At the store, the reason he confronts the robber is because he cannot deal with his life. When he says, "Shoot me" it's more of a request than a challenge, and when he calls the robber a coward he is really referring to himself. The entire rest of the movie is his flashback to the relationship and his fantasy of his worst fears (failing as a father/losing his wife and child/aliens descending and taking away everything he loves.) The very end is him in the hospital having to wake up and face his life after he suicidally confronted a robber.