There is one type of fear of sin which is very VERY basic and that is fear of punishment. Nobody likes to suffer.
People try hard to avoid pain. That is not only a human trait but even members of the animal kingdom try to avoid pain. [My ninth grade bio teacher insisted that human beings are members of the animal kingdom but I know that he was only talking about certain types of people, such as kick boxers and defensive lineman who delight in sending quarterbacks to the emergency room]. So to avoid sin because we are scared of the "potch" [Yiddish for "blow". That was the word we used growing for what we got when we went out of line. "Potchies". A PACHAD!]. that will come in it's wake is a very low level.
How can we elevate fear of sin to its more ideal state? Recognize that sin is disgusting and disgusting is abominable to the soul and abominable to existence. This abomination causes excessive spiritual anguish. The greater the amount of light in the soul, the more the stain is visible, and so the soul is prevented from enjoying its beautiful harmony with existence, with its beauty and glory, with its honor and sanctity - and fear of sin comes.
So it's not about the "potch" but about the fear of losing the splendor of your pure soul and immersing it in the spiritual feces created by sin.
יראת העונש, המדה השפלה, שבצורת המוסר הרוחני, הרי היא גם כן המדה העליונה כשהיא אידיאלית. הא כיצד, מכיר האדם את החטא לכיעור, והכיעור למתועב להנפש, ומתועב אל ההויה. והתיעוב מצער הוא צער רוחני אמיץ מאד. ולפי גודל האור שבנשמה, ככה הכתם של החטא נראה, וככה הוא מונע את ההרמוניה היפה שלה עם ההויה, עם יפיה ותפארתה, עם כבודה וקדושתה, ויראת החטא באה.
