The Prophet (peace and blessings of Allah be upon him) said: “The slave will receive a response so long as his dua does not involve sin or severing of family ties, and so long as he is not hasty.” It was said, “What does being hasty mean?” He said: “When he says, ‘I made dua and I made dua, and I have not seen any response,’ and he gets frustrated and stops making dua.”
[bukhari&Muslim]
The Prophet (saws) has said in a
Hadith narrated by Abu Huraira: Make Dua and be assured of being answered, and know that Allah does not answer a Dua from a careless heart which is not concentrating.
[Tirmidhi]