I think you mostly learned it from your Mom and are just copying that. Too, I was thinking that it might have to do with not being comfortable being angry/upset? You might want "confirmation" from others that it is all right to feel what you feel, that it makes "sense". Sometimes with big emotions it can be hard to hold them in ourselves, they can feel kind of scary and make us anxious?

I would figure out something meaningful to you to remind you and help you learn other ways of dealing with what is going on in your life? Maybe find a little "box", you can keep on your desk at work (pencil box?) and/or home to remind you to "put" personal experiences/situations you are working with in it instead of broadcasting them? Maybe when you could carry a little notebook and when you get the urge to talk, write it down in the notebook instead?