How does a person know that God is pleased with him and loves him, and that his deeds are accepted, if he prays, fasts, performs his religious duties, and does not commit sins?

A Muslim knows that Allah is pleased with him through his adherence to his religion, his steadfastness upon the truth, and his piety. For Allah loves the pious, and those who say, "Our Lord is Allah," and then remain steadfast—no fear will be upon them, nor will they grieve. Moreover, Allah does not grant religion except to those whom He loves. So, whoever Allah grants religion to, He has indeed loved him.