Hazrat Moulana Ashraf Ali Thanwi (rahmatullahi ‘alaih) once mentioned:
In today’s times, the statement, “This mouth is unworthy of making du‘aa” is commonly heard from people. A person once came to me and expressed the same feeling, saying that he was unworthy of making du‘aa. In reply, I asked him, “Do you perform Salaah? Do you recite the Kalimah?” When he replied that he does perform Salaah and recite the Kalimah, I said, “When you are worthy enough to perform Salaah, to fast and to recite the Kalimah, then why are you unworthy of making du‘aa?” This feeling, that you are unworthy of making du‘aa, is in actual fact created by Shaitaan in his effort to mislead you. He wishes to deprive you of the barakah of turning to Allah Ta‘ala in du‘aa. Similarly, your nafs does not wish to exert itself in any work. Therefore, whenever it is told to do any good work, it looks for some excuse or the other to avoid doing that good work. (Malfoozaat Husnul Azeez pg.128)
Source: Ihyaauddeen.co.za