Update: I did it, after the meeting I handed in my resignation letter. I gave them 1 week. They tried to double my salary and asked me to give them 2 more months. Obviously I refused. Thank you everyone for your advice!
I've been working at my current firm for about a year and a half, and I'm completely overloaded and overworked. This job has left me physically and mentally ill, and I'm feeling incredibly depressed. Despite trying to resign three times, my managers and directors have always convinced me to stay because I needed the money for my family.
However, I can't do it anymore. I'm overloaded to the max, and I don't even have time to apply for jobs elsewhere. Tomorrow, we have an overall meeting, and they plan to ask me to be the new team leader, taking on responsibilities for multiple companies and teams even tho we're extremely understaffed and therefore all of the work will be solely on me and I can't do it anymore.
How do I tell them in the meeting, in front of everyone, that I will be quitting? Just a quick note: this is my first job, and I am not very confident. Please send me your advice.