In plain words
Man, who lives in this world with certain ideals, must blend them with spirituality. We see it every day from daybreak. The postal postman. He gives one cover at one house and goes on. At a second house he gives another cover, belonging to their address, and goes on. In this way he keeps giving each person a cover according to their addresses, and goes on. In one house they tear open the letter, look at it, and all burst out wailing. In the second house all look at theirs and burst out laughing. Is the postal peon the cause of one house laughing and another house crying? No. No. It is the effect of the letter that came to that household. That is the chief cause of this crying and this joy. In the same way, God is a postal peon. You experience the joy and the sorrow of the letters that come to each of you according to your own karma; but God has nothing whatever to do with it. That is why, "karmānubandhīni manuṣya-loke": man cannot escape experiencing the fruits of the karma of the good and the bad he has done. That is the belief of the people of Bhārata. But without trying to recognise the special worth of their own Dharmas, or their distinction, or their substance, they simply blame God. This is merely the first stage of Ajñāna. To set about laying the faults on God, without trying to recognise one's own faults oneself, is Ajñāna. The peon brought and gave you the letter that came to your address. Beyond that, it is you who think over the joys and sorrows of the one who wrote it and fall into joy and sorrow.
When you were born from your mother's womb, no necklaces at all are to be seen: not a single string of fine pearls, no chain of pure gold upon the neck, no necklaces of gems shining, no emeralds and rubies set, no necklaces of diamonds glittering, no gomedhika stones along with them. There is, there is one garland on your neck: gathering in it the karmas of former births, Brahmā gives it to you and sends you forth, a heavy garland, a necklace strung with all your karmas.