I think that assertiveness is one of those. My God, I still remember just devouring the whole slew of assertiveness training books in the early 70's. It made so much sense to me, and gave me so much permission to say NO.
Then there is the whole co-dependent and boundaries topic area. Working with battered women, then getting involved with ACA (Adult Children of Alcoholics) and just being completely in love with the whole "set your boundaries" idea, that I needed to get my self-worth only from myself and not from others.

And yes I know it's not either or, but still...I need to look.
We often forget to re-evaluate, to take a look at our patterns and routines, because they come from somewhere, and that was the past. How do they fit with our present?