to survive on a starship, to survive on the enterprise, chekov has to learn a different way to utilize his limited supply of energy. because of course 75%, 80% of the time, he will have a perfectly normal uneventful shift, and he will get off his shift and go eat dinner and spend time with sulu or go to his room and work on math problems or whatever.
but there are plenty of times when something happens during his shift, something that requires a lot more of him than a normal shift. times when he has to respond to a lot of orders in quick succession, when he has to think very quickly and get accurate results from his thought process. times when he has to change what he's doing rapidly and react instantly to sudden stimuli.
and he can do it!! he's okay at it. maybe not great, okay, maybe not perfect. sometimes even if he knows what he has to do he's not able to actually do it without orders. sometimes he makes mistakes, sometimes he gets panicked and freezes up and needs help. but he can do it.
the problem is those situations eat up a lot of energy very quickly, and he's not really used to that. before being on the enterprise, he generally rationed his energy pretty carefully. he would spend it more or less evenly throughout the day, maybe have to forgo doing something fun if his day was stressful, but mostly he made it to the end of the day before running out of fuel.
it's different on the enterprise, when emergencies happen. when they don't it's fine, but when they do he uses up all his energy on that and crashes hard afterwards. if it's bad enough or goes on for a long time, he starts drawing on resources he doesn't really have, and it can really throw him off the next day, and the day after that, and the day after that if it's serious enough. he can do it, but it comes at a pretty high cost sometimes.
he adapts, though. and so does everyone else. he's the only bridge crew member who won't be pulled onto an emergency shift when he isn't scheduled, and kirk schedules him mostly on alpha shift. when things do happen on his shift, he usually gets his next one off; usually if an emergency lasts longer than his scheduled shift he chooses to stay with the rest of the crew until it's over, but kirk or spock make sure to have another navigator on standby in case he needs to go, and to check in with him to make sure he's holding up okay.Â
after emergencies mostly he goes back to his room and lies on his bed staring at the ceiling. he tries to eat something if he can - a lot of times when he can't manage going to the mess sulu will bring him something.Â
chekov/everyone caring about him and helping him when he needs it
otp tbqh
