I'm not so sure about this. We all know the downsides of identity, but it seems to have its upsides as well - generalizing from one example, I know that I have a much better track record trying to change my behavior through "x is what a good {boyfriend|student|Green Team fan|Star-Bellied Sneetch|...} would do" than "x is a wise thing to do." (Although perhaps someone who self-conceptualized as wise would have an easier time.) My guess is that people who say (accurately, as far as I know) that Stoic philosophy has helped them benefited not so much from exposure to the advice that one shouldn't make one's happiness dependent on external circumstances (surely everyone has been so exposed) but from actually motivating themselves to do it by leveraging their identity as an adherent of Stoicism. Mutatis mutandis "rationalist," and so on.