Eagles Over the Kennebec

There would be practical disadvantages if you were the only immortal in a nonimmortal society (and you didn't want to live your life as a lab rat of the CIA or some other such organization while they tried to find out why you were immortal and if they could make somebody else immortal), which would be hiding the fact that you are immortal in a society that requires passports, driver's licenses, social security numbers, etc. I think the TV series "Forever Knight" and the Highlander TV series and films, as well as the Jack Harkness character on Dr. Who/Torchwood TV series addressed that aspect fairly well. Those also addressed another downside to being immortal, which would be knowing that every time you made friends with someone or fell in love with someone, you would always have to leave them before they got wise to the fact that you didn't age, and that you would always and inevitably outlive them. That could get awfully hard pretty quickly. You'd either have to be spiritually very resilient and be able to accept that reality, or be a hermit or antisocial as heck (so you wouldn't be inclined to make friends or fall in love in the first place) or be a psychopath and be devoid of empathy. We already have a small taste of it with our pets --every time we get a pet, we will eventually have to go through losing them. Imagine what it would be like to have to abandon your friends, or worse, your spouse and children (if you could have them) over and over and over again.