“When they came to Jesus, they saw the man who had been possessed by the legion of demons, … and they were afraid”. 
Mk 5:15 NIV 

There are different kinds of fear. A student goes into an exam room in trepidation about what the paper will contain. That is fear. A person wakes up in the night after a nightmare and lies there afraid to close his eyes again in case it returns. A woman gets a big dog as a companion out of fear of being attacked by intruders. A man leaves his wife and she says, “I fear he won’t come back”. She means she doubts whether he will or not. Panic, alarm, phobias – these are all different kinds of fear. So is awe and reverence. 
The townsfolk who went out to see Jesus and the man who had been cured of his legion of evil spirits were surprised, confused, in two minds whether to believe it all or not. They were also apprehensive since the destruction of the pigs carried all manner of implications as well – including financial ones. Maybe part of their “fear” was also awe in the presence of the special man who had brought order out of chaos in the demoniac’s heart and mind. It could have included a measure of fear that the man would suddenly revert to his former state and terrify them all again. 
Have a certain amount of healthy and reverent fear in the presence of Jesus Christ. He is the King of kings and the Lord of lords. A too casual approach may cause you to miss the dignity and majesty of his person. But by his power and love he can transform your fears into courage and confidence. 

Lord take my fear away and fill me with faith and courage.