I'm planning to inform my manager on Thursday that I want to hand in my notice on Friday. They don't work on Friday so Im going to tell them earlier. I don't have a back up job, I'm just genuinely so burnt out at this one that I don't even have the capacity to apply elsewhere and want a break. Thing is, I'm leaving when it's extremely busy and there is no one to take over my job as I'm the only one who can do it. It is only me and my manager on our team and nobody can fill in. Me and my manger have somewhat of a good relationship but there's been tension at times as they can be quite pedantic and high strung.
I'll have a month notice period so they'll probably hire someone to replace me but even training them to do my role would be incredibly difficult/time consuming for my manager who simply does not have the capacity besides the work they do. It would set back the workload immensely as there are many deadlines coming up (we work in the legal department). I know my manager will be hugely upset and disappointed that I'm leaving at a critical time but I can't handle it anymore.
How can I avoid the fallout and keep good relations? I'm worried they won't understand especially because I'm not leaving to another job which they would understand more.