How do you know which feelings to keep to yourself and which to share?

This question isn’t about me, even though I’m muddling through personal stuff right now and I’m trying to figure out how to differentiate between my feelings and reactions to a current situation. So, I do not intend on sharing details of my situation or my feelings within this question. Also, I do not intend on answering questions about my situation or feelings. (Not that I do not want to share or do not plan to share. Instead, I want to learn something about how other people interact with their feelings and situations. This is more of a “how to” quesiton, not a “please share private details” question.

I’m curious to hear how others tell the difference between feelings affected by their current/recent situation vs. feelings resulting from physiological issues. I’m not looking for specifics (i.e., I’m not asking for folks to share private, personal details), rather I’d like to hear the concrete actions or processes others undertake in order to identify their feelings.

I realize it is often impossible to separate the two (e.g. physiological feelings interacting with situational feelings, one magnifying or minimizing the other, etc.). With this in mind, I’m not expecting to hear a checklist of “these feelings belong entirely to physiological” and “these feelings belong entirely to situation.” Instead, I’m hoping to hear something to the effect of, “when I am in a stressful situation, this is how I interact with my feelings so that I know which feelings I need to keep to myself, and which feelings I need to share with the person involved in the stressful situation.”