If something matters to me I try to imagine how I would feel if I lost it and do that until it doesn't matter anymore. It's not a perfect process.
I still enjoy experiences but I'm ready to lose them and try to see the positive side and find purpose in making the right choice given the information I have. I don't castigate myself for making a choice that was bad in retrospective as that choice already happened and I have no control over that. I can just try to improve in the next one.
Thinking about loved ones who are suffering or are dead is probably the hardest thing to process but you have to keep your sanity somehow and get over things, eventually. If you don't do it now, either time will do it for you or you'll go insane.
For death, it's pretty simple. You won't have to make any choice when you're dead. What's to fear about something you can't control? Just accept it already.
As the serenity prayer says: "God grant me the serenity to accept the things I cannot change; courage to change the things I can; and wisdom to know the difference"
Sooner or later you have to accept death, with acceptance you will be able to enjoy the gift Called "present"
If you're religious, you'll either go to hell or heaven. Or reincarnate. This depends on if you're a good person. So be a good person, every day, until you die.
It also grants some freedom. You die because you give your last bit of food to someone. Or you die because you got an allergic reaction to vaccines. Or you jump on a grenade. A noble death leads to a noble afterlife.
If you're not religious, then why worry? Supporting your family? Get life insurance. Write a will.
There's a theory that we will become dust and our consciousness becomes pure energy, one with the environment. That's pretty cool, isn't it?
Anything I left out? Identify it. Plan for it. If there's one thing you can control, this is it.
And in case that fails, I’m signed up for cryonics.