I take it that when you said, " Unfortunately, I have a wife and bills and can't afford to do that." you meant that the unfortunate part was the bill part!
Getting old(er) is not for the faint of heart to be sure. Personally, I always try to stay positive, even in light of things like you are going through.
Given that, why not think of this as an opportunity rather than a loss? For instance, now you are forced to look at new ideas. As such, in reading what you do well and get good results almost every time, I did not pick up any passion? On the other, I did detect a whole lot of passion regarding the wildlife. Who says you can't do both, or even find something else that you would love that can also pay the bills. Think outside the box. There are so many opportunities that you probably didn't think of because you didn't have to before, surely, something can pique your interest and passions again.
Thanks for all of the replies and to be more specific, I am a part-time pro, but due to some annoying health issues (disc problems in neck, worn out knees, and torn rotator cuffs) I have all but quit the paid work this year. I would like to get back into things once I get through rehab/surgery, which should be done in the next few months.
The thing that transpired this was from looking at my work as I prepare to enter the North American Nature Photography Association (NANPA) Showcase contest. I look back over my nature and wildlife work and I realize that it's nowhere near the level of the pros who place in the top 250 of the contest and wonder if I'm wasting my time doing nature/wildlife. If I could sit out in the wilds every day, I would probably get better shots, but nature photography is about luck as much or more than anything else. Unfortunately, I have a wife and bills and can't afford to do that.
On the other hand, it seems like some of the other work I do comes very easily and I get very good results just about every time I shoot. I used to shoot fashion/models back in the film days and made good money doing that, but I'm in a small city now so that's somewhat out.
I don't mind being a generalist, but part of me would like to be really good at one thing instead of okay at lots of things. Maybe I'm just making too much of this but I'm frustrated with the quality of my work.