Jeff' Olson' book has such a wide application.
Personally, I had used the slight edge unknowingly or invisibly over conservatively thirty years when I first started the gym program, gradually increasing my cardio and weight training fitness level to my current age of 82 years old!
I was unaware of his book till halfway through my fitness journey.
When I started reading this great book, I realised I was following his principles of 'easy to do' rather than easy not do!
The penny dropped further during my studies of Solution-Focused Therapies when clients present their usual problem saturated narratives smothering their strengths, values and beliefs which are the building blocks of positive outcomes.
These exceptions or gaps in their thinking are the 'slight edges, the compounding propellers to significantly success, wellbeing and happiness!
Had I known the gems of this book, I would have read it well before any other self-help on the market!