Formal Methods

One of the The Most Powerful and Valuable sentence i have found in the chapter 7 of the Book The Pragmatic Programmer

But always remember that formal development methods are just one more tool in the toolbox. If, after careful analysis, you feel you need to use a formal method, then embrace it—but
remember who is in charge. Never become a slave to a methodology: circles and arrows make poor masters. Pragmatic Programmers look at methodologies critically, then extract the best from each and meld them into a set of working practices that gets better each month. This is crucial. You should work constantly to refine and improve your processes. Never accept the rigid confines of a methodology as
the limits of your world.