Unfortunately, "stop doing OT" is hardly ever an option for salaried employees, at least in the US.

Maybe I don't have enough experience out in the world, but why do you say that?

tl;dr: If you won't do it, they will find someone else who will.

Being a salaried employee is sort of like being paid by the job or task.

For example, if you mow lawns for a living you are probably paid a flat fee to mow the lawn. Neither your bosses or your customers care how long it takes lawn to lawn or even mowing to mowing of the same lawn--you get paid your $40 to mow a lawn.

Your bosses job is to estimate how many lawns you can mow in a day.

A typical boss will see how many lawns you can mow in a day then generally assign you that many lawns, maybe a few more or less.

The trouble is that often times the bosses will assign more lawns then you can handle in your day--they have an idea that you can't get it done, but they don't really care about that because they know that as a conscientious employee you will do your best to mow all those lawns, or as many as you possibly can, in that day even if it means your day is longer.

You know that your boss will use the fact that you didn't finish mowing those lawns to deny you a raise in your per-yard rate at the next review.

So, the reason you keep doing this is because you know that as shitty as it is to mow these lawns and never be done, there is a slim chance you'll get a raise "next cycle", and even if you don't get a raise you know there are a bunch of other people who are ready and willing to step in to mow those lawns and finding another job probably isn't going to change very much you'll most likely still end up mowing lawns and still getting assigned more lawns, so you decide to stick with the devils you know.