Everything that is something had to come from nothing. Every relationship you have in your life, at some point, was not there. So if you were fine before it happened, it’s proof you’ll be fine after it’s gone.
Which is like life. At some point you didn’t live. And the world worked fine. And at some point you will be dead, and (probably) the world will work fine without you after that too. As Stan, in Monty Python’s Life of Brian, says:
What d’ya got to lose, ya know? You come from nothing, you go back to nothing. What’ve ya lost? NUFFING.’ (at 2:30)
‘Nothing will come from nothing. Cheer up ya old bugger.’
Acknowledging the temporary nature of everything is not about labelling it as insignificant. In fact, it’s the opposite; acknowledging that everything is temporary, the relationships you value, the people you care for, the experiences you cherish, the animals you love, allows you to fully engage with how special those things are right now, and proves to yourself.
But what about familial relationships? Things that you have never lived without. Well yes, you may have never lived without your mum or dad or brothers being so closely genetically connected to you etc. but I’m guessing that the relationship you have with your mum or dad now, is not exactly the same one you had when you were young. So there was a time before this type of relationship existed that you were okay. And even with brothers, sisters etc. strong relationships take time to build, so there must’ve been a time before it was so strong.
So you were fine. And you’ll be fine.