Gandalf's "advice" to Frodo is neither wise nor comforting.
At least, we don't see how anyone can find any true comfort in it.
But it's definitely not wise. It's just a truism. It's a statement of the condition of being alive, delivered to someone who is despondent in order to get them to stop whining, because there's nothing to be done besides destroy the ring or suffer the consequences.
You're just going to suffer one way or another.
"So do I, and so do all who live to see such times. But that is not for them to decide. All we have to decide is what to do with the time that is given us.â
That's really just a polite way of saying what our parents always told us:
"Tough beans. Life's not fair. You have to do your homework."
Even the "So do I" part was echoed by our parents with, "We had to do it, too. At least we're not punishing you the way our parents did."
We don't want to hear it anymore. Fuck off, Gandalf.