Holy crap, how did you not notice for that long? Was the glue just not holding right or something? I'd be freaking out about having to redo all that work, lol. What size notch were you using versus what you should have used?
Spread it right" sounds like the kind of advice that leads to a bigger mess later. You might save a minute on the trowel but lose an hour fixing a bad bond. Some textbook rules exist because people already tried the shortcuts.