For all of last year I was known to my ROTC shipmates by my last name only. I made a deliberate effort to get to know everyone by their first names as well as teach them my own, because it felt odd to pass someone on the street and be greeted by "Hey, Roy!" instead of "Hey, Liam!" I began this year by insisting that they use my first name exclusively, since I was no longer to be a part of the Service, but apparently that was just too weird.
Now I understand that there will forever be a very small group of people that know me as Roy, and I suppose I should consider it a privilege. There may be a dozen Liams lined up in a row if someone calls our name in a crowd, but I'll know any of my shipmates instantly if they call out Roy. I think that's something to treasure.