There are many good reasons G-d created fear.
One reason is in order to fear violating G-d’s wishes and incurring punishment. Indeed we find that people in the generation before the great flood lived even up to 800 years or more and their fear of G-d was minimal as they said, ‘I’ve got many years before I meet my Maker for a reckoning’.
That generation also didn’t yet have sicknesses and the result was terrible: “For all flesh corrupted its ways before Me” (Genesis 6, 12). The entire world turned their backs on G-d with the exception of Noah and became corrupt and destructive. Why? The Midrash Tanchuma (Genesis 60) says this was because they were mighty people, with a bountiful abundance of food (they would sow their fields once every 40 years!) and they never got sick. When a person has nothing to fear he throws the yoke of G-d off of himself and can violate every transgression in the Torah.
The second reason is to be warned to stay away from danger. A person won’t walk at the edge of a high roof for fear of falling. Without that fear he would be in danger of actually falling. Fear of animals is similar that we are protected from the danger they pose by keeping a safe distance away.
The Mishna in Avot (3, 2) says: ‘Without fear of the kingdom (meaning authorities) a man would swallow his friend alive.” Fear of authorities makes a person stay in line not to kill or steal from others. Imagine how highways would look if people weren’t afraid of the State Troopers. Indeed in American history and the history of many nations where there was no authority like in the ‘Wild Wild West’ there was also lawlessness fraught with danger.
Fear of illness prompts people to eat healthy foods and maintain the health even getting the appropriate vaccinations to prevent getting those illnesses.
What should we fear? Does G-d want us to fear things in the world (outside of Him)?
The Talmud (Berachot 60a) brings 2 verses that seem to be contradictory. In Proverbs (28, 14) it says: “Fortunate is the man who is always fearful”, which seems to praise the idea that a Jew should be fearful and cautious all the time. In Isaiah (33, 14) it says: “Sinners in Zion were afraid” which sounds like only sinners need to be afraid. The Talmud resolves the contradiction saying that “the fear we should have is for the words of Torah we learn.”
Man should fear only these 2 things:
One: That he shouldn’t forget the Torah he learned and he should review them until they flow from his lips.
Two: He should fear the consequences of his actions and envision what they might be before deciding to take the action he is about to take. As the Talmud says (Gittin 55b), because of the story of Kamtza and Bar Kamtza, where the host had no qualms to banish Bar Kamtza in front of all the other guests at his wedding, the Holy temple was destroyed, for the host behaved shamelessly because he was wealthy7 and well connected. Lacking basic fear he threw caution to the wind and brought about the temple’s destruction when Bar Kamtza went to the Roman authorities in anger and vengeance and started the wheels of destruction that brought down our holy temple.
The correct fear is to fear sin and its consequences
A man should treat his wife nicely to be a mensch but also out of fear of repercussion from G-d. Likewise a person should measure the action he is
about to do to see if it won’t result in desecrating G-d’s name publically. In all Biblical commandments we are commanded to fear their violation for fear of the punishment that violation will incur from G-d.
There are many illustrations of this healthy fear as the book ‘The Paths of the Righteous’ enumerates in the chapter ‘Gate of Worry’: “A person should fear to pay a loan on time and not be the person the verse calls wicked as it says “a borrower that doesn’t pay is wicked”. Likewise a person should be worried if he took something from someone (stealing) and he didn’t return it. If he doesn’t yet keep Shabbat properly he should be troubled by why G-d didn’t help him keep the holy Shabbat properly, and it’s probably because he didn’t yet learn the laws of Shabbat properly.”
“He should also worry to make sure he learns Torah daily for the first question they ask a person when he arrives in heaven after he dies is; “Did you establish set times for Torah learning?” Likewise a woman who doesn’t yet dress modestly should be troubled and wonder why she can’t yet understand why modesty is so important.
Honoring your fellow man
Another healthy fear is that perhaps we aren’t being careful with our friend’s honor and perhaps because of that people speak evil about the Jewish nation. Or perhaps haughtiness or jealousy crept into our hearts.
Outside of these fears, all others are not valid and can even cause damage as Job (3, 25) says about himself: “I feared… and that which I feared came upon me.” Job was fabulously wealthy and was blessed with righteous sons and daughters. G-d’s blessings rested on his actions yet he feared: “Perhaps I will lose my wealth or lose my children or health.” He had negative thoughts which became a self-fulfilling prophecy and he indeed lost his wealth, children and health.