Praise be to Allah.
Allah is Able to do all things, and if you pray to Him sincerely, he will answer your du`a. Allah says (interpretation of the meaning):
"And when My slaves ask you concerning Me, then I am indeed near (to them by My Knowledge). I respond to the invocations of the supplicants when he calls on Me (without any mediator or intercessor). So let them obey Me and believe in Me, so that they may be led aright." [al-Baqarah 2:186]
Among the evidence that du`a may have the benefit of eliminating problematic characteristics is the hadeeth of Umm Salamah (may Allah be pleased with her), who said: "Abu Salamah came to me one day after being with the Messenger of Allah (peace and blessings of Allah be upon him) and said: 'I heard from the Messenger of Allah (peace and blessings of Allah be upon him) something that made me very happy. He said, "There is no calamity that befalls one of the Muslims and he responds by saying 'Innaa Lillaahi wa innaa ilahi raaji'oon (Truly, to Allah we belong, and truly, to Him we shall return),' then he says, 'Allahumma ujurni fi museebati w'ukhluf li khayran minha (O Allah, reward me in this calamity and compensate me with something better than it),' but Allah will do that for him."'" Umm Salamah said: "I learnt this from him, and when Abu Salamah died, I said, 'Innaa Lillaahi wa innaa ilahi raaji'oon,' then , 'Allahumma ujurni fi museebati w'ukhluf li khayran minha,' Then I thought to myself, Where could I find anyone better than Abu Salamah? When my 'iddah (waiting-period) was over, the Messenger of Allah (peace and blessings of Allah be upon him) asked permission to see me, whilst I was busy dyeing a hide. I washed the qaraz (a kind of dye derived from a certain plant) from my hands and granted him permission, putting out for him a leather cushion stuffed with palm fibres. He sat down on it, and asked for my hand in marriage. When he had finished what he had to say, I said: 'O Messenger of Allah, I do not want you to lose interest in me, but I am a very jealous woman, and I am afraid that you may see in me something that could earn me the punishment of Allah. I am also a woman who is ageing, and I have children.' He said, 'As for the jealousy you mentioned, Allah will take this away from you (according to another report: as for you saying that you are a jealous woman, I will pray to Allah to take away your jealousy). As for what you say about age, the same applies to me as to you. As for your children, your children are my children.' So I accepted his offer and the Messenger of Allah (peace and blessings of Allah be upon him) married me. Allah gave me someone even better than Abu Salamah, namely the Messenger of Allah (peace and blessings of Allah be upon him)."
These two reports are in the Musnad of Imaam Ahmad. The hadeeth was also reported by Muslim from Umm Salamah, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) said: 'There is no Muslim who suffers a calamity and says what Allah has commanded: "Innaa Lillaahi wa innaa ilayhi raji'oon, Allahumma ujurni fi museebati w'ukhluf li khayran minha," but Allah will compensate him with something better.' When Abu Salamah died, I said, 'Who among the Muslims could be better than Abu Salamah, the first household to migrate to the Messenger of Allah (peace and blessings of Allah be upon him)?' Then I said [this du`a] and Allah compensated me with the Messenger of Allah (peace and blessings of Allah be upon him). He sent Haatib ibn Abi Balta'ah on his behalf to ask for my hand in marriage, but I said, 'I have a daughter, and I am a jealous woman.' He said, 'As for your daughter, we will pray to Allah to make her independent, and I will pray to Allah to take away your jealousy.'" (Reported by Muslim, 1525).
I want to tell you, my brother, that the sincere person whose du`as are answered has to be completely honest with Allah in the way he strives to rid himself of bad characteristics and to acquire good characteristics. If you want proof of this, it is to be found in the hadeeth of the Prophet (peace and blessings of Allah be upon him): "Whoever seeks to be patient, Allah will give him patience." (Reported by al-Bukhaari, 1376). He (peace and blessings of Allah be upon him) also said: "Knowledge comes by learning and patience comes by making oneself be patient." (Reported by al-Daraqutni and others; classed as hasan in Saheeh al-Jaami', 2328).
Allah has created the means of getting results, so you must pay attention to the laws of Allah that govern His creation. Use the means of acquiring good characteristics and avoiding bad characteristics so that you may get the results you want. You must strive hard and call on Allah. Allah will not betray the hopes of His slaves or cause their hard work and efforts to be lost or wasted.