The question "what does being grateful for the blessings of the lord of the universe" was answered by professor Hussein Ansarian as he said: Imam Reza (A.S) says: saying prayers is appreciating and being thankful for the blessings of the Lord of the universe and the one who doesn't say prayers is ungrateful of Almighty God; in other words, he is saying: I don't say prayers, because I don't accept you, I don't say prayers, because I don't love you, because I don't want you. This is what not saying prayers really means.
source : erfan.ir