Too many times people take it upon themselves, or are instructed to make up for the shortcomings of others. There are too many yes men. The people who are making life hard for others are constantly passing the buck and they need their feet held to the fire for anything to change.
Someone forgot someone was already off today and they need you to come in instead? Not your problem. Someone gave you something to do at the last minute and you need to scramble to get it done? Sorry, you aren't a miracle worker.
My personal favorite: Management has been ignoring your calls for more help but deny that it is necessary and dump all the extra work on the remaining employees. For too long, we just accepted it, but recently, me and a coworker REFUSED to stay for “surprise” OT and now they finally admitted they needed to hire 3 more people.
They obviously can't fucking hire anybody to replace you easily and if they're spiteful enough to fire you anyway for admitting you aren't superman, then you're better off working somewhere else.
I used to be one of those people who would try to be the BEST WORKER, thinking that it would pay off down the line somehow and SPOILER it didn't! I only got more work. I was the fastest, always staying busy, always helping others, cleaning up after lazy people, always the first one people come to when they need a favor. But all I did was make my boss and boss's boss look good.
It's about goddamn time they are seen for what they are, failures that are being propped up by good workers.