"The Dip"

Hello, 

I recently read "The Dip" by Seth Godin, and am interested in hearing what your views are on this book. Does anyone have insight on how to identify if your "dip" is too large to invest in? In the book Seth references that some dips are just not realistic to succeed and the better choice is to quit, but how do you identify this? 

I'm a project manager and my current projects would easily be considered beyond my experience. Our PMO is still developing and I am lacking mentorship. 

I am seeking advice on identifying when I'm in over my head and should take a step back to maintain my reputation and gain the right experience for the point I'm at in my career. 

Thanks!