vpwphoto: Mid-life crisis when you wonder about the meaning of life and if anything has value after all. Try a good read of Ecclesiastes.
Another thing that helps is to give away your photography. By that I mean, print out some of the work you like, frame it and gift it friends and families. The appreciation and thanks you will get will kick you up to a higher level. And when you visit their homes and see your work on their walls, you will have a sense of immortality. Just like when you think about your kids. Good luck.