This is the root of my health anxiety. It came on when my daughter was born because suddenly someone relied on me almost completely and that thought totally overwhelmed me. I couldn't stop thinking about what would happen if I was gone. Now, she's 5 and I still get this fear only it's both about how sad she would be if I died and also what a tragedy it would be to miss out on her life since she's such an amazing person. When I get into a big spiral about this, though, I try to think that if my fear is missing out of life/the people in my life then the best thing I can do is not waste time worrying about when I'm not here and start focusing on right now, when I am.