When you are frustrated, you have every right to show the frustration straightaway. But it needs the right composure, of mind and thoughts, to keep it all to yourself and come out responding in the other way. It’s not that by doing this you are controlling your emotions. Rather, by doing this you are giving the situation or the other person a benefit of doubt. It shows a side of you where you have accumulated the due respect to others or circumstances. Certainly, it ensures the slight introspection edge you entertain for yourself, which has always been proved as a success mantra.
Frustration not shown is never a problem, neither for you nor for any other, but the frustration shown could be the start of a problem. Beware.