“It is a curious thing that at my age one begins to dread the dropping of acquaintances. Like a tree, which it is said must be spared any more cutting at its roots, one feels that one cannot bear to lose any more of one's friends.”
— Agatha Christie
Simplified Meaning:
As people get older, they really don’t want to lose friends because it feels like losing a part of their life, just like a tree that can’t handle losing any more of its roots.