It happens, but you sorta have to be a f**k-up. If you're a f**k-up, then go ahead and worry. Otherwise, there are hundreds of residents out there who never did "honors work" in med school who nevertheless plod through residency successfully. (BTW, you can count on "messing up" during residency. That's why we have a residency training period these days, instead of leaping directly into practice where no experienced folks are hanging around to stop you from killing people.)
This is a bit naive. There are programs out there that *brag* about kicking out a resident or two a year. Not because there is anything wrong with the residents, but because the program is malignant. Believe it or not, there are some sad sacks in running programs who are so screwed up themselves with a dash of viciousness in their personality that they take delight in destroying other people's lives.
Mostly you do not get kicked out for "messing up." You get kicked out for political reasons. You piss off the senior resident, or the program director or the hospital brass. They can make you gone even if you're the best resident to trot in the door. I've seen it happen. And if it does, not really a whole lot you can do about it.
Case in point: midwest community hospital fired 7 residents from its IM program in 4 years. That many residents get in that far over their heads? I doubt it. Significantly, of these 7, five managed to get into other residencies, (2 surgery, 2 IM, one rad onc) despite the PD's public vow that they'd never work in medicine again.
So, do your homework, be careful and choose your programs wisely. You'll do fine, but when interviewing keep your ears and eyes open, listen for subtle clues. Be very aware. A malignant program will hide those who will be honest with you. Figuring out in advance which program is good is difficult. If you do find yourself in a malignant program, remember it's only 3 years, keep you head down, your mouth shut and then when you get the certificates and licenses, tell the whole friggin world about how bad the program is.
In the meantime, learn what you can, and keep your helmet on and your head down.
If you find a good program, that's great too. Enjoy life, congratulate yourself for choosing wisely, and when you're done tell the world it was a great program.
Good luck, you'll do fine.
Oh, and ahh sacrament, Where's the evidence? I mean, where's the prospective randomized controlled studies that show that we need 3-7 years of residency post internship to stop you from killing people? APNs are saying just the opposite as they lobby for more independence in practice. And they are proving it in rural clinics.
Where's the beef buckaroo?
There's nothing that I've ever found that demonstrates a GP, with current CMEs is less qualified or competent than a board eligible internist in terms of cost of care, clinical outcomes, diagnostic abilities or less capable of reading Harrisons. You figure board exams are costing around $2500 per applicant, and now with MOC/Recertification that the specialty boards are pushing, x say, 100,000 doctors, makes for a whole boatload of money for the boards, and someone's gotta pay for that, without demonstrated benefit, since the people most likely to be not current are those who are grandfathered. But again I ask, where's the evidence?