I read a book many years ago whose title was the same as this post. It didn't take, I need to read it again but no longer have it. I've been in a bit of depression off and on lately. I've been trying to put my finger on the source.
I have a very nice life and feel guilty for not just being ecstatic. I work almost all of the time and hardly take vacations. Not all of my work is billable engineering or photography work, much of it is dedicated to accomplishing my dream. My dream is to make a good living doing the thing I am most passionate about. That thing is helping others using my writing, photography and video production skills. I also just like helping people by creating opportunities to spend time with like-minded people, share insights, etc.
I think part of my current sadness comes from two things, maybe three:
The photos were taken during my bonus afternoon walk today. I just had to get out, into nature and try to capture some of its wonder.