We are hardwired to have fear, whenever we feel threats to our well being. If we weren't, early man wouldn't have survived all the obstacles they faced. Fight or flight kept us from being extinct, by now.
Overwhelming fear is unhealthy, but fear itself can motivate positive action. However, the degree to which we respond to perceived, or real threats, is very individual.
We should never criticize, or make fun of someone having more fear than we might. It's a personality and psychological dynamic, that depends on many (often learned) variables.
It can sometimes be controlled, but it's not voluntary. Just like someone having a panic attack is not voluntary. It's quite painful for them.
So if you have family, or friends in a meltdown, just listen to them and let them purge their fears. They're not likely to be discouraged from them, but will find comfort in knowing they have support, that someone is trying to understand, and, that they won't be abandoned.