How do I know that a prayer has been answered?

Supplication (Du'a) is an act of worship that Allah has commanded us to perform and has promised to answer. The supplication of a Muslim will not be lost. Either Allah will grant him what he desires in this world, or He will store its reward for him in the Hereafter, or He will avert evil from him through it. Thus, every supplicant receives an answer through one of these three outcomes. The answer may not be exactly what was supplicated for; rather, Allah may compensate him with something better, such as averting harm or storing it for him in the Hereafter. Therefore, a Muslim should frequently engage in supplication, while being keen to fulfill its conditions and avoid its impediments.