I imagine it is more common than you think. My wife loves her job; it has been the only thing she's ever wanted to do since she was a kid. And now, as the job gets harder and she gets older, and for the first time in her life questions whether she wants to do this for the next 20 years, she is faced with the reality that this is the only professional job she has ever had. And if she left this, what on earth could she possibly do, at 47 with 2 kids to support?
While fear was a predominant emotion for me, it was not the most debilitating. It was more a symptom of my anxiety and depression, which I was ultimately able to get a handle on. I wish I could explain how I was able to do so. Part of it was meeting my wife, but I was already getting myself back on track before we met. She just helped keep the ship on course.
Fortunately for us and our joint incomes, I did not feel as tied down to my job as I had when I was single, even if I was still afraid of trying something else. Eventually we had kids, and that was able to give me a level of happiness I had never had before, and a greater reason to work, as it wasn't just me I had to ensure had a roof over their head and food to eat. A few years ago I was able to do something new, which I might not have been able to when I was single. It ultimately failed and the company dissolved, but we were able to weather the storm with my wife's income keeping us afloat until I got a new job.