We need fear of Hashem to achieve our purpose in life. Fear of Hashem helps us identify the attacks of the yetzer hara and defend ourselves against them. Fear of Hashem motivates us to overcome the body's natural laziness, complacency, and procrastination. Fear of Hashem protects us from not becoming cynical through not fulfilling the Torah that we learn. Fear of Hashem defines us as human; without it, people are dangerous animals. Fear of Hashem frees us from our base desires. Fear of Hashem makes Hashem real enough to love. It is impossible to fell live for Hashem whie inundated by the cacophony of life's daily struggles. Fearing Him allows us to elevate Him and His will above all other considerations in our lives. It is then that we are able to have a real relationship with Him. Knowing we are constantly being watched 24/7 makes it easier for us to avoid transgression.
In addition, fear of Hashem protects us from self-destruction. Every transgression adversely impacts us in this world several ways. First, our self-concept as spiritual beings is crucial to success in the conflict between our soul and our body. When we identify with the soul, we naturally expect that we will act spiritually. Conversely, when we identify as the body, we can't help but expect to act physically.
Each transgression or indulgence affects the clarity of our self-perception as a soul, and therefore, each time we listen to the body and follow its directives; it encourages us to identify with the body and its desires. This weakens our resolve to follow the dictates of the soul in the future,
Second, each transgression we commit diminishes our self-respect. Self-respect is the pleasure that comes from fulfilling our responsibilities and obligations. Each time we are negligent in fulfilling our responsibilities, our self-respect is compromised, which leaves us feeling degraded.
Third, transgressing also weakens our self-confidence. Each time we fail to do the right thing, we lose confidence in our ability to exercise self-discipline and withstand the temptations of the body. But each time we remain strong and resist temptation, we strengthen our belief in our agility to overcome future challenges.
Fourth, each transgression distances us from Hashem. Closeness to Hashem is attained only by listening to Him. Fear of Hashem is a powerful tool which empowers us to resist temptation, thereby protects ourselves from self-destruction and, conversely, strengthens our self-concept as spiritual beings, builds our self-respect and self-confidence and brings us closer to Hashem.
Filling the heart with fear of Hashem is a powerful tool to use when plagued with improper thoughts and desires because if helps rid ourselves of these desires.
Fear of Hashem awakens one to life's incredible beauty and meaning. Focusing on the opportunity to gain eternal reward or suffer terrible punishments makes each moment of life incredibly rich and meaningful. It motivates us to achieve goals we otherwise would not think attainable.
One builds his fear of Hashem by thinking about it regularly.
One who serves Hashem with the basic level of fear serves Him for personal benefit, to reap the rewards given to those who fear Him and follow His will and to avoid punishment meted out to those who transgress His will. That person is considered a tsaddik - a righteous person. A person serving Him based on awe of His majesty does so selflessly, without consideration of personal benefit. This is the ultimate level of the commandment of fearing Hashem. A person who achieves this level is considered a chassid. – one who serves Hashem above and beyond the basic level of serving Him.
(Rabbi Noach Weinberg z"l of Aish Hatora, quoted by Rabbi Yitzchak Coopersmith in "Constant Connection" page 205-211)