I view the poly relationship style in and of itself an exercise in pushing ones comfort zones on many many levels.
I think its even more drastic coming from a long standing monogamous marriage or partnership in which one partner has an epiphany.
Growth vs pushing ones comfort zone I m not sure how to quantify those or if they are related. Having to give a eulogy to a packed church with out breaking down blew through the comfort zone wall by a mile. No growth detected just tapped to do a difficult task. Speeches and toasts could bump up in the comfort zone area if I was forced on the spot to make up something."come on get up there and be funny " no pressure there