And to the parent comment--I'm fine, thanks for the concern :)
I also felt some stress when busy, but that was less because there was a lot to do and more because I had someone who was expecting it to be done in an unreasonable amount of time.
The second time was different. I was working two more than full time jobs (academic and running startup that was taking off). I literally did nothing for a couple of years (2010 - 2012) but work, eat and sleep. At the time I didn't feel stressed (I was comparing how I felt with the early stress times), but I was under a lot of stress. I only realised when I quit my academic job.
[1] Noting General Electric, Jeffrey Immelt, Jack Welsh and the collapse of the financial system that led to getting rid of finance as a profit center.