Shaykh Fawzan answers
May Allah give you good. The sister says: I supplicate oh Shaykh, I supplicate to Allah saying: “Oh Allah verily I ask You to hasten for me marriage.” Is asking Allah to hasten your dua from the reasons the dua will not be accepted?
Shaykh Fawzan: Requesting for Allah to hasten the dua is not from the reasons that dua will not be accepted.
When the Prophet, peace and blessings of Allah are upon him, supplicated for rain he said:
Oh Allah! Pour down upon us a wholesome rain, now not later. 
This is because there is benefit in the supplication being hastened for the person.
As for being hasty in supplication it is for the person to say: “I supplicated and supplicated and I was not answered.” Thus they give up making dua. This is what is prohibited.
Translated by Rasheed ibn Estes Barbee
 Sunan Ibn Majah, Chapter 154. What Was Narrated Concerning Supplication For Rain, Hadith Number 1269