> Today's

This is false. The observation that being too nice and trying to please people is counterproductive, and putting it into self-help or pop-psych books, goes back to at least the 1970's.

For instance, see the book Creative Aggression, The Art Of Assertive Living George Robert Bach, Herb Goldberg [1974]

That stream of thought was probably the foundation of the whole "me" decade of the 1980s and all that followed.

Oh yeah, and then of course there is material like the writings of Ayn Rand, The Virtue of Selfishness [1964]

If we go centuries back we have Machiavelli's The Prince and whatnot.