Sometimes it's just time to move on, especially if a job is becoming physically painful to perform. That's your body telling you it's not enjoying it any more.
Admittedly, I haven't had to do any sort of real manual labor in over 15 years. I own two companies which are successful, and those afford me the ability to pretty much do as I please. I still need to keep tabs on my business interests, though.
So, that said, I'm considering selling the smaller of my two companies. About 50 people work there, and every single one is a stellar employee. Many of them are dear friends, as well. I've just lost the passion I once had for that industry and, when I go into that office, I feel like I'm spinnin' my wheels. I've got two employees who are considering purchasing it if I decide to let it go.
I turn 60 next year, and I know I don't want to turn 65 being a business owner. I'm in good health, I'm devilishly handsome (to those who matter to me) and have a smokin' hot Puerto Rican girlfriend, 8 years my junior, who isn't going anywhere. We've worked hard to get where we are. It's time to enjoy the fruits of our labor...