The fact that this idea would cross your mind is not at all unusual in America. However, here in France, where I am enjoying some R&R before I lead my annual women's retreat in Provence on Sunday, it is not commonplace to change careers at midlife, or at anytime for that matter.
French students must decide on a discipline or career path at 16 or 17 years of age. The idea of an "undeclared major" in college is unheard of. One must decide on a direction early on, and that decision essentially casts their professional fate.
While Americans enjoy the cultural norm of changing jobs and professions about 4-5 times on average during their lifetime, the French tend to remain in their "métier", or profession until retirement—whether they enjoy it or not. Perhaps that is why the French put more emphasis than Americans on non-work activities over which they have more control--like vacations and eating well.
So, if a shift in jobs is in the works for you, be grateful that you are in a culture that supports this type of a life change. Perhaps you could have the best of both worlds in this transition: enjoy a change to more satisfying work as well as put adequate attention toward the non-work parts of life.
Even though I'd find it impossible to make a living here as a career counselor to the French, I have an appreciation for the balance they seem to achieve between work and life.