It’s easy to activate someone’s flight/flight/freeze response when your having difficult conversations. Once someone is activated, you’ve lost your audience. They're no longer listening because they're busy keeping themselves safe.
State your intention before launching into the difficult topic. It will help you get clearer on what your trying to achieve. It will also be kind on the other person’s nervous system. They will more likely be able to listen and co-operate. This will move you both closer to the desired outcome.
A combination of a past of difficult relationships, trauma, and conflict can make our internal alarm systems more tweaky. It's a bit like those fire alarms that go off just from the toaster. Respect the other person’s alarm system: it’s just doing it’s best to keep the person safe.
Equally you might be on the receiving end of someone dumping their woes onto you. Ask them what their intention is. It might just confuse them out of projecting their internal dramas onto you.