How do I deal with my guaranteed end to everything I hold dear?
I'm so sorry to hear that... can't imagine what to do.
Are you referring to a terminal illness or just death in general?
Ignore it. You're not going to give a shit when you're dead either.
By realizing that in all reality no one needs to worry about death, that we're all going to be just fine. Remember, we are all where we belong.
Everything has a beginning and end. We are born out of this world and return to it eventually. Try to enjoy this dream while it last anon.