I changed careers (corporate to non-profit, financial services to mental health) at age 43. It's been stressful, yes, but also invigorating. There are days when I think, "I don't need this," but overall, I'm really glad I did it. I actually feel really grateful to have had this opportunity, and have learned a lot and grown a lot. It was hard in the beginning not feeling competent, but by the six-month mark, I was starting to feel comfortable, and I think being outside my comfort zone was good for me. I don't want to become complacent, or just put one foot in front of the other.
Also, I have drawn clear boundaries in this job and my family comes first, and that has been fine. It was actually nice to start a new job with very clear priorities and knowing what I was willing to give, and also OK if that turned out not to be enough for them (we could part ways amicably). I have three kids (two with special needs) and a parent with cancer, but it's all been pretty manageable.
I'm very glad I didn't just let the clock run out in my other job--I feel more alive now.