From time to time, you may find yourself listening to a person
complain about his/her life, or some part thereof, and not know how to
respond. Or you may find your response doesn't work out well. What
should you do?

Let me tell you a story.

Once upon a time, a company that I worked for had a woman come in to
give a series of workshops on teamwork and group dynamics, etc. She
spent an entire session on the question of responding to a troubled
person. The first thing she did was to solicit possible responses from
the group, and compiled a list of about 15 different ways to respond:
Sympathy, offering suggestions, saying the person should stop
complaining and take a positive attitude, etc. Then she went through
the list and pointed out that each and every one had a fatal flaw.

Then she said that the one, unique way to avoid all the fatal flaws was
a technique called reflective listening. This technique consists
primarily of acknowledging
what the other person has said without adding any content. The idea is
to assure him/her that you have heard and understood what he has said.
In particular, you reflect back the person's emotions. So your side of
the conversation consists of phrases like "that must have been awful"
and "you must have been angry" or "you must have been terrified." If
you Google "reflective listening", you can find a lot of material.
So I went home armed with this knowlege and listened to my wife rant
about this or that, and stuck in a "you must have been angry" or the
like, and the very first time I tried it, she said

"Don't try that crap on me!"

(I hadn't even told her about the workshop.)