Lean In - to what?

Sheryl Sandberg's book is all over the place. I'm putting off reading it, because I read all these amazing quotes from it everywhere, and am worried the book as a whole can't live up to the best-ofs (inclduing from the Economist, quoting Sandberg "the most important career choice in your life will be whom you chose as your partner" - or perhaps it was marry, or husband, I can't recall whether she was that progressive...). But sometimes, after a day with slightly fruitless meetings at work and as a school parent rep (today being one of those days), I wonder what it is that we are supposed to be leaning into. Isnt a better question sometimes whether we should not be trying to make things more interesting, more something-suitable(ish)? It's probably not possible without leaning in first. But patience has never been my greatest strength...