The actual meaning of Dua is to call. Dua is an act by which we get close to Allah (swt) we should always keep in our mind that we are nothing and the one who has all power is Allah therefore we are always in need to Him now our duty is to call our Lord but we can’t calculate which one of our Duas are accepted and which one has not accepted just like a child Who totally rely on his/her parents without any doubt and asks what he/she wants but it is his/her parents has to decide what is better and suitable for their child and what is not good and yet it is not a appropriate time to make his/her wishes true. So we should always remember our Lord by our Duas and this will make a strong bond between Creation and Creator.
Asking Allah for things is in itself a good action. Continue asking Allah, but the reason for delay could be a number of things that are unknown to us.
We have a narration from Imam Sadiq (as) that states “if one were to see the reward in the hereafter for all of the prayers that were not answered in this world he would wish that none of his prayers were ever answered at all!”
Sometimes a request we asked for may not happen and we think it is bad but in reality it might have been good. We may have prayed to get a certain job, but in reality that job might have been bad for you.
It happens sometimes that you want to go somewhere and your tire gets flat. You get mad because you will be late, your tire costs money and takes time. Maybe if you would have not had the flat you could have been in an auto accident but you avoided it.
So, Allah may be protecting us from something unknown to us and we should thank him in all situations.
We should always seek Allahs forgiveness as well. We see that one of the keys to having your dua accepted is true and sincere repentance. We see that we read in Dua Kumayl: