Musar על מגילה 44:23

He refers to this lack of confidence that G–d will have to listen to our prayers by stating that – as distinct from Joshua – who relied on his worthiness, we do not rely on our worthiness, לא על צדקותינו אנחנו מפילים תחנוניו לפניך, "we do not submit our pleas before You because we rely on our righteousness." Instead we rely only on G–d's grace since the Torah mentions (Exodus 33,19) that G–d reserves the right to show grace and mercy to those whom He chooses (even if they do not deserve it). I have already explained the string of expressions commencing with the repeated use of the word מה.

What is meant here is something that I have explained elsewhere in connection with the verses 1) "Serve the Lord with joy!" (Psalms 100,2), and 2) "Serve the Lord with fear!" (Psalms 2,11). When a person gets ready to pray he should consider that he is totally insignificant, no more than a drop of evil-smelling semen, sinful and obstinate and thus he will become fearful and feel ashamed. Hence his eyes will be turned downward. After that he should contemplate the greatness of the Lord, how exalted G–d is, etc. These feelings will produce joy within him. Joshua son of Nun was of the tribe of Ephrayim. We find that G–d had granted both Moses and Joshua the attributes of חכמה, and that both of them prostrated themselves when praying. Our sages, pointing to the example of Joshua, are on record that any scholar who is not certain that his prayer will find a favorable response must not prostrate himself when praying.