Talk to some elderly people and ask them what aging is like. The answers will be all over the map, of course, but I'll bet many, if not most, will mention loneliness, a sense of loss and confusion.
Think about the changes we've seen in the last two centuries, or the last half century, or since 9/11. It's simply hard to keep up with the dizzying pace of change.
Moreover, no person can know everything. Even if you're immortal, you're probably going to be puzzled by a generation of young people who are more hip to the latest Internet conventions and memes than you are. It might make you feel a little alienated.
What kind of social life are you going to have? Are you only going to date people who are closest to your age - like in their 90's?
If you don't feel a special connection with Nature, count your blessings. Mother Earth is spiraling downward. Young people may be relatively unaware of this sad state of affairs, because they haven't lived long enough to see many major changes. I was born in 1955, and I can see the changes very clearly; it's scary.
If you're immortal, you'll be forever comparing the world you were born into with the current world order, which is probably going to become more perverted with time.
You might be able to make new friends, but you can't replace your parents, siblings and other relatives. You may feel a little lost and confused without them.
Frankly, I think it would take an exceptional person to experience immortality without going insane. I suspect immortality would best suit people who are introverted and have interests and passions that keep their minds occupied in lieu of a meaningful social life.
In fact, philosophers might be better suited to immortality than most people. But imagine if Plato, Kant, Machiavelli, Descartes, Buddha, Confucius and Jesus were all living today. The passing of centuries would only enhance their wisdom, and they could grow even further by sharing ideas with each other.
Imagine Jesus and Machiavelli exchanging notes on their iPhones. Cool.
But I'll bet all of these great thinkers would mourn their youth, when life was so much simpler and the environment so much more pristine. I suspect at least some of these seven immortals would eventually take a cue from Socrates and opt for suicide.