A man’s feeling that he’s ignoble and insignificant in front of God’s greatness and that he has no right to rebel or disobey is one of the psychological motivations that help in stabilizing the servitude in self and feeling it inside. This psychological feeling of humility in front of God’s greatness and His great nobleness, with the fear and respect in the believer’s self, results a feeling of submission, obedience, and fondness to the worshiped (God), fearing from losing this love and getting anger and torture instead.
Fearing from losing love and connection with God has a positive effect on the believer's self, same as Al Raja’(hope in God) does. Having hope in God and not being hopeless from his mercy, sympath, affection, and justice makes a complimentary work beside fearing from Him to regulate a man’s personality and direct it towards God.
A believer’s feelings always grow towards God when having hope and waiting for God’s sympathy away from hopelessness and despair that close a man’s doors of hope and prevent him from reform and changing attitudes.
These motives of fearness and hope have psychological impacts and effective power on man’s behavior, his engagement in good deeds or being far from doing bad deeds.
This is because fear and hope form in the deep of a believer’s self two equal equations that share motivations and a man’s complete behavior.
Al Imam Mohammad Al Baker (pbuh) explains the impact of these two motivations in a believer’s self and the psychological relation between them by saying:” There is no believer except he has two sources of light in his heart, the light of fearing God and the light of hope in Him. If these two are measured, no one will exceed the other. God has gathered these two traits when describing those whom He praises, saying: they call their God in fear and hope. And He said: they supplicate Us in hope and fear”. 1
Al Imam Al Sadek (pbuh) enlightens the aspects of this context and enriches it when saying: “Fear is the heart’s guard and hope is the self’s mediator. He who knows God well will fear from Him and have hope in Him. They are the two wings of faith that a believer flies to God through them”. 2
From this short discussion about the motivations and psychological factors that play a role in having a real servitude in self, we can recognize that love, fondness, fear, and hope are the psychological motives that react together in the deep self. They push a man to be fond and connected to God almighty. They also push him to work with all his abilities of thoughts, feelings, and work to gain the acceptance of God, take his reward, and be sincere in His servitude.
Worship and Slavery, Al Maaref Islamic and Cultural Institution
 Jame’ Al Sa’adat for Al Naraki, part 1, page 253
 The same source page 254