You shouldn't hide your emotions as that is actually unhealthy for you mentally, but being able to choose to express them is possible, for me it was recognizing what was triggering my emotions and coming to terms with that, and although I still struggle to not be emotional (I don't think it ever truly goes away) I understand why I am and so I'm able to express myself accordingly even though I may be feeling pretty broken inside.

For example I was recently denied a position at my workplace, my manager and the manager I was transitioning to made it seem like it was a done deal even though I had accumulated points for a write up due to attendance (attendance points systems are garbage by the way), apparently they have moved people before even though they had them, well you know the rest, even though there were clear examples of them disregarding it for others, for some reason they enforced it on me, that was hard to not express how I truly felt, but I was able to keep my composure and just thanked the managers for the opportunity, they did say I can re apply in June but at this point I don't know, that felt so disheartening, like I know I'm expendable but that truly made me feel like I wasn't worth anything to them as a employee, so you can probably surmise how I felt and what I wanted to express at that moment...