10 Downsides to Immortality
10) Global Decay
9) Relative Time Reduction
8) Mental Decay
7) Severe Social Divides
6) No Value
5) Monotony
4) No Social Progression
3) No Retirement or Welfare
2) Useless Criminal Punishments
1) Violent Death
If not any of these, the death of a star will happily engulf both you and the planet you happen to live on. You could of course escape into space, but not much awaits for you there; unless you enjoy drifting in endless darkness until the end of time.