It is a source of continual angst to me that I'm not teaching college physics at a small college. It's my calling, it's what I'm supposed to be doing. I sort of made a mistake by going to a research University (that really wanted to be even more of a research University, and was transitioning away from a balance in valuing teaching), but at the time it was the only job offer I had. If you want to be faculty in physics and astronomy, you're lucky to get in in the first place.... I would have been happy if I could have kept that job. Alas, I failed, repeatedly, to get NFS (National Science Foundation) funding. I tried reinventing my research program in an attempt to make something that would better match the preconception of the funding agencies. Ironically, this was away from Dark Energy. However, I was the only professor at my institution who was part of a large collaboration, and funding agencies aren't interested in that. Indeed, astronomy panels (at least 7 or so years ago) were suspicious of large collaborations in general. But, still, no luck. And, in my last few years, the knowledge (confirmed repeatedly by my department chair) that no NFS funding meant zero chance for tenure begin to weigh more and more heavily on me, and I became more and more dispirited, which made it increasingly difficult to produce any papers and to get good proposals written. I was in a death spiral.
A year before I left Vanderbilt, I applied for jobs at small colleges, and got several interviews. I did get one offer, but sadly, for family reasons, I wasn't able to take the job. The next year, I applied again, but only got a couple of phone calls, no actual interviews. Now that I'm out, barring some particularly interesting angle, there's very little chance of my being able to get back in. There are just too many young hotshots out there with solid research records, no gap, and who aren't already over 40. This isn't to say it's inconceivable, but I've been on search committees, and I know what happens when they see somebody who's more than 6 years in and not a superstar.
I can't help but wonder, though, if things might have been different if the economy had crashed several years earlier, and if we didn't have a president openly hostile to actual science in the white house. In a speech to the National Academies, Obama announced that there's going to be a huge increase in the budget for the NSF. Mind you, only 1 in 6 grants were being funded, so even if it goes to 1 in 3 (which I doubt will really happen, because assuredly some of that NFS doubling will go to various big projects and other "rich get richer" sorts of things), it's still difficult, you still spend a lot of your creative effort banging your head against thew all. So, I might have had exactly the same outcome. However, when grants were turned down, sometimes NFS program officers could only say they didn't know what to say, because money was so tight; in previous years, they might have tried to help people applying figure out how to better tune their grants. At 1 in 6, it was a complete crap shoot.
I can't help but wonder if it might have been different. If I was, in part, the victim of bad timing.
"A man is not old until regrets take the place of dreams." --John Barrymore
The fact that I'm 40 doesn't so much make me feel old. The fact that I'm 40 and not spending my primary full-time-job creative effort on physics and astronomy, together with a realistic assessment that I'll be able to get back into the sort of faculty job that I want, makes me realize that many (not all) of my primary dreams have in fact been replaced by regrets.