Well, that sucks.

That’s the very first place to start.
Sympathy is a healer, it coagulates the bleeding.

Well, that sucks.

It won’t drag them down if you validate their pain. It doesn’t mean you condone how they got into the pickle, or the fact that they may be bitching about the same chump after seven years, or that they done gone did it again — or any of that fairly useless judgement and assessing.

Just nod, and say,

Well, that sucks.

Do not immediately tell them that:

it’s all for the best.
it doesn’t matter in the grand scheme of things.
the universe has a bigger and better plan.
it’s better to fail now rather than later.

And for the love of God, do not tell them that there’s a gift in the lesson.

All those theories are true. And they should be communicated, emphatically, repeatedly.
But not quite yet.

Don’t leap over their pain.
Just see it.
And say you see it.
And go from there.