What are some downsides to immortality that most don't think of?

I'll start off with one, Being upset about a breakup that happened hundreds of years ago.

Edit 1:

• Heath death of the universe, Death of the sun, etc, does not count. I feel like focusing on this is an overused point.

Edit 2:

• Loneliness does not count. I feel like we all know immortality means you'll miss people and lose them.