Wow, that was a fascinating article J. G.! And it summed up exactly how I feel sometimes. 40's are tough in certain ways. I thought the curve concept was neat.
I also thought it was interesting how some of the results were the same regardless of what "phase" of life you were in in your 40's. I'm 45 and my kids are 20 and 17 (almost 21 and 18). I should be in the sweet spot of my life, and in many ways I am. But I catch myself musing over things I wish I had done better with my kids, or done differently with my career. I'm looking forward to my 50's now after reading this article!
And I do think the the KEY component to happiness in this phase (and any phase) is gratitude . . . for it all.
ETA: Forgot to answer your question! No, I wouldn't say I've had a crisis. More like existential angst sometimes. :)