When you feel that someone is heading for a crash try to deescalate the situation. Hear them out, hug shit out if it feels appropriate. Drop pretense, take a step back and get some perspective. Let things slow down for a bit and understand that it might take some time. Personally I can be a bit of a sponge with emotions, but I want to say that most people are. These things work both ways, so be calm when people around you feel alarmed.
short term, long term is harder