It usually comes in stages for me.
The first is a feeling of euphoria, excitement or adrenaline at the prospect and activity of dressing up, going out, and just being me for a while...
The second is a realization that you're no longer concerned with the fact that you're "dressed up", but that you're just out and about and existing, dealing with normal day-to-day concerns of eating, walking, working, talking, etc...
Then it's a realization that I've gotten to that stage of comfort and warm happiness washes over me...
At least that's how it goes for me with public presentation anyways. I still have to dress up as some semblance of a boy for work every day, so the cycle starts over every weekend, lol.