That seismic rumble you feel is 100,000 postdocs and grad students nodding their heads:
The ones I’ve seen thriving in Cambridge, apart from geniuses (there are a few), are the guys who cling to a simple ecological tenet: Find your niche, where you are indispensable, and keep it in your claws at all costs. This means basically that these people do always the same thing, over and over again, simply because it’s the lowest-risk option. I could have done the same (I was pretty skilled during my Ph.D. in a quite obscure but interesting biophysics experimental technique) but I thought that doing science properly was also about learning and broadening your expertise. How wrong I was.
You can imagine yourself what does it mean also for research in general: Nobody takes risks anymore. Nobody young jumps and tries totally new things, because it’s almost surely a noble way to suicide your career.
There is a second option, which is bare survival. You go from postdoc to postdoc, perhaps end up as a long-term researcher somewhere in some tiny university or irrelevant research center (like CNR in Italy) and basically spend your time with a low pay, working on boring projects, crippled by lack of funding and without any hope of a reasonable career (because the career path is taken over by the hawks above described), nor any hope of stability in your life.
Notice that, again, both paths do not offer you any guarantee of sort. You can arrive to tenure track (itself an achievement) and being kicked out after a few years, thus ending up as a jobless 40-year something, with a family probably, too old to compete in the market of real jobs. And bare survival is not easy as well.
Experiences vary, but nearly everyone I know who 1) started grad school more than three years ago, and 2) has not yet found relatively permanent, gainful, and financially remunerative employment within their chosen field, can vouch for similar feelings – even when you’re lucky and surrounded by genuinely caring human beings.
(h/t to Spivak for the link.)