Same with partners, pets, really, everything. All is temporary. It’s important to be completely cognizant of this when adopting a new pet, deciding to be exclusive with a new partner, taking a new job, and so forth, that, you will most likely out-live it. It will go away, somehow, sometime.
All the good times, love, building something, come with this price. That’s why it is so important to be fully present when you have it, because someday, you won’t.
I tell my kids (all young men) that I love them, every.damned.day. Because I know I will have to let them go. I give my cats (and my dog while she was still alive) as much attention and love as can fit in a day, because they will most likely die before me.
A life of no regrets, which includes not regretting not being fully (as possible) there for who and what we love, is the best we can hope for, and that will still evade us. But we try anyway with this sisyphean task, the lesser suffering.
Two choices: run/hide from this reality, this eventual pain, or, accept it and embrace and cherish as many moments as you can, while you can.