Choosing is a big one. Something I learned later in life about emotional maturity and controlling your emotions is that it's just choosing to feel an emotion.
Like, feeling angry for longer than I needed because I didn't know how to make the choice to feel happy or calm.
Of course there's more nuance to it but I agree with choosing
No, people are not choosing emotions. You can show them or not, but it is not true that one "chooses" them.
Emotions are not controllable or choosable but our reactions to them are trainable. One good technique for this is mindfully observing and labelling the emotion until it goes away; not trying to change it but also not acting on it. With practice one can observe the emotion subsiding within a minute or so. This, eventually, leads to less emotional reaction overall because we're taking away the habitual pattern of the mind to constantly react to everything it likes or dislikes.