He that swells in prosperity will be sure to shrink in adversity.

How a person behaves when things go well tells you how they will behave when things go badly. Someone whose sense of themselves inflates with good fortune has tied it to circumstance, so the same mechanism runs in reverse the moment conditions change. Steadiness in either direction comes from having your footing somewhere the weather cannot reach. That is built during the good stretch, not the bad one.

Notice how much of your current mood is borrowed from how things happen to be going. If the connection is tight, find one source of steadiness that does not depend on results, and attend to it while you do not need it.