The literary meanings of phrase prayer means requesting in a humble manner. A little pondering about this definition would reveal:
Because the reality of prayer is requesting and beseeching - an act of the heart and that is internal - therefore, a prayer which does not come out from the heart or in other words from a negligent heart in reality, is not a prayer.
Because prayer is a request in a state of need with humility and is not like other requests or demands; therefore, a prayer or request which is not accompanied by need and humility too will be far away from the reality of prayer.
Since the request and pleading inevitably should be accompanied by hope, it must be understood that hope is an essential part of a prayer; therefore, a prayer which is not accompanied by hope or is accompanied by hopelessness will not be regarded as real prayer.
Since for acceptance of prayer and fulfilment of wants one may trust only someone Who knows about our genuine wants as well possesses the power of their being materialized, therefore, the supplicant must have firm faith in the knowledge and power of Allah (the Glorious, the Exalted), to whom he is beseeching for fulfilment of his own needs through prayer; a firm faith about His knowledge and wisdom as regard to his needs; as well as His absolute power and authority to grant them.
Since humility and humbleness in front of elderly personalities differ in accordance with their status, i.e. it may be that what is considered as humility and humbleness in front of a certain respectful personality may not be regarded sufficient in front of a very great respectable personality. And since Allah (the Glorious, the Exalted), happens to be Greater than all the great personalities, therefore, one should do his utmost to show his humility and humbleness in front of Him. Because requesting and pleading before such a Magnanimous and Glorious Lord without his permission and consent would be impolite and stubbornness, which is in contradiction with obedience and humility.
Therefore, request from Him should not be without His permission; because of His Love and Benevolence towards His creatures, He had given us such a permission, and has asked us to present our requirements and needs at His threshold, and beseech Him for their grant as the Holy Qur'an says in the following verse:
"And when My servants question thee concerning Me, then surely I am nigh. I answer the prayer of the supplicant when he cryeth unto Me. So let them hear My call and let them trust in Me."
- Holy Qur'an (2:186).
Since requesting or begging in reality couldn't be anything other than goodness and blessing for the supplicant, and because a human being does not comprehend his real good and bad correctly as Allah (the Glorious, the Exalted), says in the Holy Qur'an:
"Man prayeth for evil as he prayeth for good."
- Holy Qur'an (17:11)
i.e. as he strives for his good and blessing also endeavours for his bad and evil (in his imagination considering it as good) even though this goodness might be decorated with evil, as has been narrated in the book Misbah al-Shari'a as follows:
"There is nothing (to be asked) except Allah's nearness and countenance. It is up to the supplicant not to open his tongue except for good and welfare, and should not ask Allah anything other than goodness and blessing, and should never include harmful requests in his prayers. Secondly, if the prayer is not granted, he should never be disappointed and never be suspicious about Allah's promise: 'I answer the prayer of My servants' and should consider that whatever he has asked in his prayer unconsciously, might have been harmful and undesirable, because of this very consideration Allah has not granted it and instead has stored for him other blessings."