There are people who just can't stop expressing and showing their fear for something and showing excessive anxiety. Most of these people do not really know they are actually undergoing paranoia. Paranoia is medically explained as the process of a disturbed thought. It may mean something like delusional to many and cannot be cured, but it can actually be prevented, sad to say, its something hard to control and therefore incurable for it only occur in ones mind.
I have had dealings with people having paranoia attacks when I visit hospitals and see patients from horrific accidents. Patients with the attacks scream like theres no tomorrow. They shout at every person they see and after a while, they will just crumple their body on one corner hiding their face and occasionally looking at the doctors faces. They look very scared. You can see how irritatedly they react whenever someone touches them.
Paranoia can be prevented. But you have to help yourself before it works. You have to convince your self that fear is non existent and it is only in your mind. Stop thinking of bad situations, bad memories or experiences. If there is a persistent dream or something like an apparition showing in your sleep, then try praying before you sleep. If you are not a believer, well, try believing in the idea of Supreme God. At least that helps you boost your confidence that there's someone who can protect you where you are at rest.
Seeking professionals dealing with the said problem is also a great advise. Always think that if you can't solve your own problem, there's always someone you can go and lean on. Say your problem. Open up. Speak everything about what you are thinking. Your fears, your happy moments, everything.
Self introspection and self reflection is the key to a healthy mind. Think positively and learn to control your cognition. Afterall, you are the ruler of your mind, you are higher than your brain, and you make your own thoughts. Control it and relax.
It's all in your mind. Its all in how you control it.