How do you decide what to trim vs what to add when markets fall?

This is something I struggle with, honestly. During downturns, I know trimming matters — but that’s exactly when emotions kick in and I stop following a clear process. I’ve made this mistake more times than I’d like to admit. I’m trying to think more in terms of **opportunity cost**: If I add something new, what should I reduce or let go of? I’m curious how others handle this: * Do you have a **simple process** for trimming? * Is it mostly **rules**, **gut feel**, or a mix? * Has anyone tried **writing this down or systematizing it** in any way? * What has actually **worked** for you over time? * What clearly **didn’t work**? Not looking for stock tips — just trying to learn **how people think** when decisions get hard. Would really appreciate hearing different approaches from the community .