Immortality is worse than death...
1. When you're immortal, humanity will continue to evolve, while you stay the way you are. Give or take a few million years you will become a freak.
2. NOBODY must find out, lest you be subject to properly inhumane treatment. Take a guess at which governments would want to harness the power of immortality.
3. You will go freaking insane... Assuming by immortality you mean that you can't get sick either, so Alzheimer's or dementia would not be a factor, but you will still go insane. You will have infinite lifetimes of experiences and boundless knowledge. Your brain (as amazing as it will be) Won't cope, and will break down. So when you wish for immortality, better wish for a super brain too.
4. Everyone you will ever, or have loved will die. So you can't get attracted to anything, and I mean anything. Over a period of millions or billions of years, the things you love will decay and become lost.
5. You'll eventually get trapped somewhere. Picture it, you fall down a well. That's it. You are now down there for x amount of minutes, hours, days, weeks, months, years, decades, centuries, you name it. You may get found, but this is a short sighted view. Think of this... Humanity has gained the technology to space travel. You are in a ship, it explodes, you will be cascaded out into the blackness of space. What the shit do you do then? Wait millions of years until a astral bodies gravitational field picks you up? Then what? You're stuck on a rock that probably is inhospitable to 100% of life. Great, enjoy your immortality great insane freak sage hermit of a small rock in the outer rim. You can spend your days training small monkey boy space travelers that happen to pick up your life signs Karate.
There is no 'if' that all this will happen, because it will happen. It's the science of probability. When you have an infinite lifespan, infinite numbers of things can happen. Can you guys really handle that?