Never apologize for showing feelings. When you do so, you apologize for the truth.

An emotional reaction is a piece of accurate information about your state, and apologising for it treats the information as an offence. That is worth separating from behaviour, because some things done in a strong feeling do warrant an apology. The feeling itself does not.

The next time you catch yourself saying sorry for having been upset, try describing what happened instead. I found that hard, or that mattered to me more than I expected. It is a small change in wording, and it interrupts the habit of treating your own responses as something to be managed out of sight.