I think that the composure comes with the thinking and knowing the problem. Here I am not implying that some one don't thing in the ring, but if he is going to find the hot water again in there it is already to late...

The first step is knowing the technique, then make sparring with some one who is not going to take your head off... Pick some basic stuff like breading, moving, blocking and straight punching and build upon this. The problem with boxing is the variety and if you try everything at once you are doomed. Start with the basics and think over every step you take. If you know then there will be the composure.