Fearing Allah (the Glorious, the Exalted), beseeching him with tearful eyes, and lowering head upon his threshold are the etiquette of servanthood; in addition to bringing plenty of favours and blessings also provide background for prayer's acceptance. Following are some traditions.
It has been narrated in a tradition:
"There is a bottleneck passage between Paradise and Hell, and except those who shed tears out of fear for Allah's wrath, no one else would be able to pass through it."
It has been narrated from the Holy Prophet [s]:
"Allah has sworn with his Splendour and Majesty that My servants do not know the value of shedding tears and crying; are not aware that for their crying what heavy price and sweet rewards have been stored; for them I have provided special palaces in My vicinity, and there is no partner to share it with them."
It has been narrated:
"On the Day of Judgement there is no eye which is not tearful, except the eye which was tearful in the world because of Allah's fear; there is no one with eyes full of tears because of Allah's fear, except that Allah will forbid his body parts from Hell's fire, there is no face with tears of Allah's fear flowing upon his cheeks, but Allah will make it immune from disgrace and abjectness; there is nothing in creation but has its definite dimensions and weight, except a tiny drop a tear shed for the sake of Allah's fear, that through this drop Allah would silence the oceans of His wrath; and if in a community (ummah) a single servant sheds tears, Allah would bestow forgiveness upon the entire community for the sake of that servant's tear."
Of course, there are plenty of traditions about this matter.