One of the most significant concerns I've had about choosing a career in medicine is one that is seldom discussed among doctors. Those that I shadowed back in college were (for obvious reasons) very reluctant to broach the subject, and this is one area I never completely understood.
But, combine overworked schedules with sleep deprivation, and it just looks like a recipe for disaster. How easy is it to make a mistake in practice that you end up getting sued for?
It's easy to make a mistake that gets someone hurt. Some mistakes can get you sued without objectively hurting someone, and sometimes mistakes can lead to horrible outcomes (like death) without you getting sued. You should be more worried about medical errors than getting sued, because to some degree there is nothing you can do to totally protect yourself from lawsuits, but there is much you can do to improve care, regardless of the setting.
Physicians who are unwilling to discuss medical errors are doomed to suffer them. This is why any good department and residency program will have M&M conference at least monthly (morbidity and mortality conference), to discuss cases that went poorly, decisions that were incorrect, and systems issues that lead to poor outcomes. These conferences are so important to the medical community that the content of these conferences have been deemed inadmissible in courts of law (although this protection is less airtight than it should be).
Physicians are humans and are fallible. I am a good doctor, and I have made mistakes. Some have been pretty big, and others are so insidious that unless you are constantly re-evaluating yourself, you won't catch them. Choose not to double cover gram-negatives in a septic patient with PNA after > 7 days of intubation? Depends on your antibiogram at your institution, but this could lead to a poor outcome (like death), and could have been a potentially avoidable issue. Take a patient off coumadin for surgery without a dalteparin bridge and see them stroke out? It happens, and there are justifications offered on each side.
So, yeah, it is easy to make mistakes, but we all do the best we can, try to learn from our errors (or decisions that turn out badly). You can't be so paralyzed by fear that you don't do your job. There are so many things that can go badly even if you do everything right, so you basically just have to resolve to be dilligent, get as good a training as you can, learn from every patient, and try to evolve and incorporate the most current data into your practice.