Yeah, I actually have a problem with the whole quote.
"The flow of time is always cruel."
So, just to expand a litte bit, I've been reading some Buddhist stuff lately. A big point I've gleaned is it's not change that causes suffering, it's our attachment to the way things were. So to say, "the flow of time is always cruel," seems like a matter of perspective and in my view, an unhealthy one. That's not to say I don't understand why Zelda feels that way. Basically everyone she knows has probably been killed in the last seven years and the land turned to ash.
"A thing that does not change with time is a memory of younger days."
Ok, I'm in my mid-30s — not super old, but not super young. My memory of younger days does change! With age, I get additional perspective about things and feel differently about those things as a result. Sometimes, out of the blue, I'll remember stuff that I haven't thought about in years.