I was given the best bit of advice by one of my RAF instructors when I started to flap and panic.
Be like a duck - calm and collected on the surface, giving the impression to everyone that you know what's going on, but paddling like hell underneath. slowly but surely, by trying to portray a calm outlook I started to be calm inside.
I am always keen to get things done quickly and enthusiastically and this can often result in things looking panicked (not sure that's a word?) or rushed. I was also told a bit of advice by one of my TR instructors on the 757, "sit on your hands, count to 3 then do what you were going to do" this inevitably has stopped me making a countless number of rushed errors in the past. After all, if it's not on fire or in decompression - what's the rush?
Things will get better with experience - just remember, you wouldn't be where you are now if you weren't any good.
Take a deep breath count to three and try again.
Good luck