1. Poor vision. If my vision ever declines enough to need them, I'll probably just try to fake it that I can see. Sunglasses annoy me, and there's no way I could ever touch my eyeballs to apply or remove contacts.
2. Lack of energy. I already need a good 6-8 hours more sleep per week than I used to. It will be frustrating not to have the energy to do the things that need to be done to get ahead in life. And it will be more depressing to feel the urge to choose sleep over success.
3. Cancer. It seems that it's pretty much a guarantee that you'll be hit with some form of cancer if you manage to live long enough. Which kind will it be? Waiting to find out will be the worst game of Uno ever.
4. Rectal/prostate exams. Eventually these become a part of your annual medical regimen. I'm not sure the diseases they might help diagnose and cure are worse than the tests themselves.
5. People around you dying. Death is the most frightening musical chairs contest ever. Each time someone close to you keels over, you've not only got to deal with life without them, but once again stare into your own existential void.