What are the reasons for not feeling complete solemnity (khushu') in prayer, despite reciting the prescribed remembrances (adhkar) and maintaining ablution (wudu')?

Humility (khushu') is the spirit of prayer, and without it, prayer becomes mere lifeless movements. Among the things that help achieve it are: frequently seeking refuge in Allah Almighty and supplicating Him, pondering over what is recited from the Qur'an and dhikr, and feeling Allah Almighty's praise for the humble, and His linking the success of the believers to their humility in their prayers. Allah Almighty says: "Successful indeed are the believers those who humble themselves in their prayers" (Quran 23:1-2). Also, tasting the sweetness of conversing intimately with Allah, and feeling that one stands before Allah and that Allah is aware of what is secret and what is manifest.