1.) Your family and friends would die off because of old age or illness, as will their children and grandchildren, while you persist, leaving you with severe emotional tramau, become lonely or causing you to disassociate with humanity.
The people blithely shrugging this one off are tools. They most likely just don't realise the impact others have on their lives and what their absence or the knowledge of their inescapable doom will do to a psyche. I think the best scenario here would be a person just learns to become a transient and move on and start a new life periodically, trying to forget the old one.
2.) Severe boredom, since there's only so much stuff that could be done to pass the time. We're talking potentially billions of years plus existence people
Again, totally true, boredom and loneliness do not bode well for the human mind. People spend much of their lives bored. We have to remember what Schopenhauer said here, "It is absurd to look upon the enormous amount of pain that abounds everywhere in the world, and originates in needs and necessities inseparable from life itself, as serving no purpose at all and the result of mere chance. Each separate misfortune, as it comes, seems, no doubt, to be something exceptional; but misfortune in general is the rule." (Studies in Pessimism)
We often measure our lives in narratives that we relay to each other. Mostly these narratives are about frustration and suffering and unfairness. Unending life is unending suffering. To live is to crave and strive, moments of peace and contentment are few and far between. You've been sentenced to aeons of loss and having to put up with yourself as you get frustrated and fail at things, even though you've got less justification for failing than anyone else alive.
A scary aspect of this is also that humans are creatures of habit, so an immortal would likely end up as something of an OCD mess as habits accrue. There's a song by Nine Inch Nails called "Every Day is Exactly the Same" in which Trent conveys the sense of sameness and futility and boredom that comes from routine life. People feel pointless and unnecessary and in a state of living death now
, with tragically short lives, what will they feel when given millenia of the same sunsets, the same people fucking each other over and daily frustration? You need a reason to persevere, and all things you are biologically programmed to care about are temporal by nature.
I think the sisyphean resolve of my fellow apes on this board are hubristic with little understanding of their mammalian psychology, no offence to you all.
3.) Humanity would continue to evolve around you, generation by generation, while your original, unevolved form remains, thus causing you to eventually become a freak of nature.
True enough. Likely they'll get wiped out by an asteroid.
4.) According to recent studies, time passes by faster in peoples perspective as you grow older since each moment they represent a smaller part of your life when you are older than when you a younger. A day would seem like an eternity for a toddler but around 5 minutes for an old man. Immortality would eventually cause you to percieve time in such way, when you are super old, events and people would explode around you. People you use to know would become less relevant to you. This is why Dr Manhattan became such a dick.
Also true; I remember my early life quite well and I recall that weeks seemed to take much longer, but I don't think you can extrapolate that to these scales; around adulthood, perception of time is mainly down to how busy you are, I don't think it'd automatically keep shifting smaller.
5.) You get older mentally. Imagine if your cell phone number changed every week, and every week you were forced to memorize the new one. It gets exponentially harder because all of those old numbers are still in your memory, clogging up the works. Then imagine someone asked you to instantly recall the number you had five numbers ago. Same case for immortal people. As time goes on, more and more memories pile up. Your brain can keep all that stuff organized for a while, but it's not like you can go into your brain and just delete files like cleaning up a hard drive. So useless stuff starts accumulating, clogging up the works and slowing everything down, like all those toolbars on your mom's Internet browser. Your body will be young, but you'll still be forgetting people's names and telling the same jokes to the same person twice in one day.
This depends on the mechanics of the immortality, to be fair.
6.) You can never be found out, unless you want millions of prospectors, opportunists, politicians, rich people, mobsters, scientists, and other types who want immortality coming to claim a piece of you and try to find out how to live forever.
True enough, but I don't think it'd be too bad if you "outed" yourself in the correct way.
7.) Chances are, you might accidentally get trapped somewhere and unable to move, act or do anything and unable to get help and nobody knows you are there. E.g. fallen into a cement mixer, trapped by magma which cools and harden, accidentally blown off your spaceship and drifting into deep space. For a normal person death may come as a release from such a situation, but for an immortal, not an option. Imagine being like this, FOREVER. Many people considers this as the most horrifying reason why immortality sucks
True; an unending locked in syndrome where your only hope is your mind disassociating from reality.