I've recently come to the realization that the second best piece of advice I've ever received or given is "Listen" - or put a different way "Pay attention."
Book repair can often become routine and rote. In general, most late 19th and 20th century mass-produced books are relatively similar, with some minor, but common, variations. To the person who regularly repairs these types of materials, this regularity and familiarity is both a help, and a potential stumbling block.
The structure and damage of each book that comes across your work bench is probably very much like many other books you have worked on. The similarity means that you don't need to "reinvent the wheel" with each book. With regular practice of repairing these materials, your mind and hands learn what needs to be done.
The problem with getting into this kind of routine repair is you run the risk not "listening" or paying attention to what you are working on. Your hands, which have done this repair over and over again try to force the book to behave in a way that so many other books have, but this particular book might not want to. When your hands start telling books what to do, rather than paying attention to how the book is responding to the various forces you are applying to it, you run the risk of a bad repair.
This happened to me today - and this is my confession. When I was finished with the book, I looked at it, and I felt ashamed. Okay - in the grand scheme of things, it was a mediocre repair of an inconsequential binding of an inconsequential book - but I should have listened to the book. (And no, I am not going to share an image of this repair online.)