Matthew 26:39 He went a little farther and fell on His face, and prayed, saying, “O My Father, if it is possible, let this cup pass from Me; nevertheless, not as I will, but as You will.”
Do we have a right to complain to God? Yes we do! Jesus was showing us here that we have the right to say to God that we don’t like things.
It does not mean that we should go off and do our own thing just because we don’t like what God gives us though.
Jesus made it clear that he would follow God the Father no matter how much He Himself did not relish the prospect of so much pain and suffering.
Accept what God gives you. Question it and test it. But accept it!