Turning 40 is great, actually, from my experience! When that birthday hit for me a couple years ago, I decided I was old enough and had enough life experience that I didn't have to take any crap from anybody. Not that I did when I was 39 either, but somehow turning 40 felt like I'd earned the right. "I'm 40 years old, I don't have to put up with this bulls**t!" became a mantra of sorts.