You & I have same or nearby birthdays
I'm still thinking over how to handle mine, which falls at the end of a 4 week run of very special occasions, 4 in all, incl. family wedding, family reunion, graduation, friends reunion.
I've been on P1 to knock off a little weight creep and "reboot" my head, lol. That's different than your point in the journey, but I'll offer my 2 cents in case it helps: it's much easier to go through these occasions with some rules to guide you. Not rules to beat yourself over the head with, but rules to anchor & guide your choices as each occasion comes up.
For example, at the wedding I attended, which was really a weekend, I flat out decided to stay OP for everything up to wedding cake, and have that only if not doing so would leave me feeling deprived. Knowing i had that to anticipate made it so much easier to say no to everything else, and gave me a sense of being in control, even after I had the cake. It was not at all difficult to go back to P1 after that, well, not too much : )
Phasing off is of course an option. If you do so, setting yourself some guidelines is an even better thing to do. On maintenance, it is easier to rationalize eating anything and everything. And then the "last supper" syndrome can impel you to eat even more of the treat things.
The Beck Diet Solution has some great tips to help use your mind to make it through these challenging situations no matter which phase you are on.
Congratulations on your great progress!