“Du’aa’s and ta’awwudhaat [prayers seeking refuge with Allaah] are like a weapon, and a weapon is only as good as the person who is using it; it is not merely the matter of how sharp it is. If the weapon is perfect and free of faults, and the arm of the person using it is strong, and there is nothing stopping him, then he can lay waste the enemy. But if any of these three features is lacking, then the effect will be lacking accordingly.”
(al-Daa’ wa’l-Dawaa’, p. 35).In order for du’aa’s to be answered, it is not essential to adhere to all of these points and be free of all that could prevent one’s du’aa’s from being answered. That is something which happens very rarely. But one has to try hard and strive towards achieving this.
Another important point is to realize that the response to the du’aa’ may take different forms: either Allaah will respond and fulfil the desire of the person who made the du’aa’, or He will ward off some evil from him because of the du’aa’, or He will make something good easy for him to attain because of it, or He will save it with Him for him on the Day of Resurrection when he will be most in need of it. And Allaah knows best.