Offer two cycles of prayer any time (except the prohibited times) or preferably at Tahajjud and then recite durood 7 times before and afterwards. Then recite this prayer 100 times with full devotion and concentration and imagine yourself as a beggar for Allah’s Mercy. You need to perform it daily and can offer this twice a day too to get enhanced benefits. The duration of this recitation is 21, 40 or 90 days but if you make it your lifetime routine, then it will work wonders.