NAPLEX isn't hard to pass, 75 score is easy. While I was a resident, we did have one who failed MPJE, which I admit, even I wasn't sure what I got when I left the test centre. (I got a 93, but I left feeling it could be a 70 in a worst case senario). However, know what the P&P of your residency site is, our VA allowed one more test, up until end of September to pass. Luckily, she did pass that the second time. Better to study up the first time. I was studying up at Panera bread every weekday for 2 hours on jurisprudence before the test. Overkill? Yes, but better safe than sorry. And it's free coffee refill yo! Hope you don't have any cardiac problem.
Residency wise, my experience is that it's all about time organization. If you are at a site that provide a list of research project, get in early, and pound on it before the mid year. With that, I was the resident that sat around pretty when others were scrambling for deadlines, and the only one of the four offered a job there at the end. Front load, front load, don't ease yourself in. While others might make say that residency is a cooperative sport, but it's just as much a zero sum game.
A zero sum game is one where one person's gain comes at another person's loss, as the total sum (eg pharmacy budget) is a constant fixed number. One of the biggest component of managers think about is how to get maximize the value out of your budget. If only have the money to hire one residents at year end, who will it be? So plan ahead, adapt to changes, make decisions rationally.
Morality and loyalty should not be discarded, as it has a non-tangible value that may be priceless. At the same time, do not let emotions cloud sound judgement. Weight the people vs. monetary value. Each individual must choose what they can live with. I personally would feel bad taking from someone who treated me well, at the same time, you must know what your responsibilities to your wife/family are.
Oops, sorry. Too much beer, maybe a little to ahead to matter for most new residents.