My family used to run a shelter / sanctuary for abandoned stray and puppies for decades. Became a sanctuary by accident because more and more strays started to show up / invited by their friends and we just kept caring and feeding them.

What i've learned
1) Can't save them all
2) Some needs to be put down
3) Dogs don't live as long as people, it's sad but have to accept that fact

We bury the dogs that has passed on.