100% agreed. And maybe more than 100%. I gave a talk a couple years back on "Building a Sustainable Startup" and said that it was even worse than running a marathon. Doing a startup was like developing a running career.
You can watch the video if you want, but the relevant gist is that I knew people who trained for marathons and really wrecked themselves. They did one, said "never again", and then quit running. Whereas I, a slow fat guy, took my running much more gradually, and now have been running 7 years. I even just did my first triathlon a couple months back.
Video here: http://vimeo.com/24843552