Before performing Salah you perform ablution (ritual washing) in the way prescribed by the Holy Prophet (blessing of Allah and peace be upon him). You say your prayers according to the instructions of the Prophet. Why do you do so? Simply because you believe in the prophethood of Muhammad (blessing of Allah and peace be upon him) and deem it your bounden duty to follow him ungrudgingly. In prayers you recite many things quietly. If you do not recite them or make any deviation from the prescribed manner there is no one to check you. But you never do so intentionally. Why? Because you believe that God is ever watchful, is listening to all that you recite and is aware of all things - both open and hidden. What makes you say your prayers at places where there is no one to ask you to offer them or even to see you offering them? Is it not because of your belief that God is always looking at you? What makes you leave some important business and hurry towards the mosque for prayers? What makes you break your sweet sleep in the early hours of the morning, come to the mosque in the heat of noon and leave your evening entertainment for the sake of prayers? Is it anything other than your sense of duty - your realization that you must fulfill your responsibility to the Lord, come what may? And why are you afraid of any mistake in your prayer? Because your heart is filled with the fear of God and you know that you have to appear before Him on the Day of Judgement and give an account of your entire life.