I think this needs to be said. A lot of people here mention guilt trips that managers and bosses pull when a worker gets fed up and threatens to quit. “How can you quit during such a busy time? Your colleagues will have to pick up the slack. How can you do this to them? How cruel of you.”
They use it because it works. It works by exploiting the worker's empathy.
NO! It is not the worker giving more work to their colleagues. It is a result of bad management. If it's a busy time, the manager should hire more staff. If the pay is decent, it won't be difficult.
If a staff member leaves, it is a loss to the business, not the remaining workers.
And remember it even if you aren't the one quitting. Don't bully your colleagues or guilt trip them into staying to be abused just because you don't want the added workload. It's not them giving you more work, it's the company. Celebrate their self-respect in refusing to be abused any longer.
So watch out for this guilt trip. It's precisely what abusers do. Don't let it work. Leave a toxic job safe in the knowledge that you are not harming anyone, except the company that's abusing you.