Hi Renounced,
It can be about finding a balance between self control and being able to express your feelings can't it?? Because good relationships aren't always about the "good stuff" (or wearing masks!!) but sometimes as much about being able to express some of those "negative" feelings/thoughts and how you both manage/work through those as well.
Of course with some feelings it can help to try to look at things from different angles, or more rationally, or more objectively first or even, if you need to,
with that someone else if it helps. Alongside making it clear to them that it's not personal if it's not.
And lots of different things you can try for trying to handling emotions, the harder part can be about finding things that work for
you though of course

..........but CBT (some resources are online), anger management techniques, grounding techniques, relaxation, "time out".................
But remember you
are "allowed" to have some "negative" emotions in relationships and to share them, in fact sometimes that can be
healthy.
Alison