What sort of energy are you adding to a situation? How is that having an affect on the situation?
In life it is very rare to have a conversation with something about something and not have an affect on the situation even in some small way. Be it your friend talking through an issue they are having or your boss explaining a new process they are thinking about implementing, the energy we inject into a situation can affect the outcome.
If your friend is talking about their bad interaction with someone there are multiple ways to respond. You could agree completely and even go so far as to get your friend to think they are right and that the other person is wrong. Injecting this negative energy into the situation is not really bring any real overall benefit. It may feel good at the time but not in the overall long term view. However if you add positive energy though being compassionate you may be able to help the person step back and think about things from a different perspective. This is hard to do but the payoff overall is far better than just adding in easy negative energy.
Think about the situation. How can you be a positive influence. Encourage and help where you can. Be compassionate and a great listener when the situation is negative.
If we all add positive energy the world will be a much greater place.