I transitioned in my early 30s with the intention (successfully met) of going stealth, so I've done the ritualistic "purging" of old items and so on.
But the ritual I'm really proud of is the one I performed a week before facial surgery. I went to a really nice state park about two hours away from home, with my best friend, and we hiked around all day. I collected a number of unique stones one this hike -- stones that reminded me by shape (or color, because I'm esoteric) of the various parts of my face that I was going to change: brow ridge, nose, chin, jaw, trachea, upper lip.
I went to the river, knelt down so my face was (blurrily) reflected in the water. I took one stone, put it up to my forehead, and asked the stone to take away the "spirit" of this part of my face. Then I asked the river to wash it away -- to smooth it down, as water can do to very hard things. And then I went to another spot on the river, and did the same for my nose, and so on, until the river had taken each stone.
Two weeks later, I took my first shower with my new face. As the water poured over my face, I cried... because for the first time it ran straight over my eyes, which it never could do before.
This is how I said goodbye to the past, and everything changed after that.