Answer:
If people could has absolute control of they're emotions the world wouldn't be the same. If something sad happened it would be best to stay happy so that Is what I would do. You wouldn't want to sit around moping all day.
If something scary was happening of course you would chose not to be scared because who wants to be scared. But also if you chose not to be scared there is no fun in it then. You would also need time to process and think of what your emotion should be at that moment so our reactions would be slower. You would also know what to expect whereas when we can't control our emotions a lot of the time we don't know what to expect.
The pros: You won't have to mope when your sad, you can be happy. You won't have to hide your feelings because you can control them.
The cons: If you go to a haunted house or something like that it's either because you were forced to go by someone or because you want to purposely get scared. If you were allowed to control your feelings you would chose not to get scared right?
Hope this helps!