Moni I know what you're saying about that sense of relief or liberation. I've done some exploration in public, granted mostly in a mixed presentation but even then there was that certain feeling of just conquering the fear and doing it. I've gone to my therapist multiple times dressed in various states of femme presentation (skinny jeans with high-heeled boots, dress & heels and most recently dress, heels & makeup), there is a fair amount of public exposure as I have to park on the street and walk through a wide open courtyard to her office door. I've also gone for runs in Central park and on other public trails wearing women's leggings and a sports bra, I regularly work out in hotel fitness rooms in similar gear, and I even wore skinny jeans and those heeled boots to go out to eat at a fast food restaurant. The sense of accomplishment has been great each time and the feeling of finally being able to expose a small part of the real me to the world has been satisfying and spurs me to go further.
Going to church this weekend, in full female presentation (except for my hair) will be the farthest I've gone so far but as you noted, it's a chance to say to the world in no unmistakable terms, here I am, I am trans and you'll just have to deal with me. Based on the fact that they're open and affirming, my guess is I'll also be gendered as "she, her, hers" which will be the first time in my life that anyone has applied those pronouns to me (well outside of these forums). That's a very exciting thing right there and I think my reaction to it may tell me a lot about who I really am.
So I guess what I'm saying is, I agree there probably is a certain right of passage here. It has taken me some time to get to a level of self-acceptance to even be able to consider doing this. I've come a long way in a short period from being a crossdresser in private who once in a while went out on Halloween dressed as a female to now a trans person who's still questioning but willing to let parts of the world see me for who I really am. My guess for Staci is that this type of growth is probably what your therapist is looking for in having you get out in the world for that experience.