When the events of Star Trek 2009 take place Chekov is 17.
He is seventeen when he witnesses the death of almost six billion people.
Seventeen when he saves Sulu and Kirk from slamming to their deaths but minutes later loses Amanda as the surface of Vulcan gives way & he is unable to lock onto her signal. He's a child, the death of someone else's mother is on his hands.
Chekov watched as a few elders and Spock appeared in the transporter, saw the look of devastation on his face as Spock realized his mother was now gone. They returned to the bridge and watched as a planet died, knowing there was nothing to be done about it.
Chekov's calculations were correct and it must have been the worst feeling in the universe. He had to hope - even if it was just in the back of his head - that he was wrong. He had most likely never wished for anything more in his young life.
All of this... only to then be present when Kirk forced Spock into showing that he was emotionally compromised. Hearing Kirk goad Spock with, "It must not even compute for you. You never loved her!" only to see someone he most likely admires lose his mind. No one on the bridge, except his father, could have imagined Spock in such a state.
You can't convince me that Chekov didn't internalize that. He had to have been feeling poorly as it was - to run through the halls shouting, "I can do that I can do that!" and save two men only to lose someone a few moments later in a similar situation. I know I'm repeating myself here but I remember being 17 and internalizing all kinds of things.
The one break Chekov probably had was taken from him when Spock snapped. To see Spock react logically must have been a level of comfort, even if on some level Chekov knew it was probably a lie.
And then to be the one that came up with the plan to hide the entirety of the Enterprise??? To go through all of that and still be mentally present is a kind of strength that is unimaginable for me.
I like to think that after the events of that day McCoy is making his rounds, checking in on everyone. When he gets to Chekov the kid smiles and says, "Everything is fine with me, sir."
McCoy gives him a look before responding, "Ever eager, huh? You didn't even let me ask my question."
"What question is that?"
"How are you?"
Three simple words. And Chekov's illusion he built for himself shatters.
Seeing Vulcan destroyed was bad enough. But he hasn't been able to sleep without seeing Amanda disappear from the screen, seeing Spock hit Kirk over and over with displaced rage, hearing Spock's voice shake as he says, "Doctor, I am no longer fit for duty. I here by relinquish my command based on the fact that I have been emotionally compromised. Please note the time and date in the ship's log.", or waking up scared that Spock will blame him, because why wouldn't he?
