I see panic as a state that occurs after all other avenues are expended. For some this is single pointed action, for others paralysis (fight or flight or freeze).
People who are used to working through problems have a tendency to continue to seek solutions and trust their ability to manage variables longer than people who do not have that experience. This is a compounding process in a way, because those who are comfortable doing so tend to gravitate to situations where this occurs whereas those that aren't, don't. The more practice you have at successfully solving problems under stress, the more comfortable you are in those conditions.
It's not really a courage/fear thing. People who don't panic just seem to be able to push the moment where one feels there are no options left, off longer. When they hit the wall they too will probably act in the same way.