Please be clear: you do not have convince God to help you. God loves you. And God gladly helps and gives to you. If something is good and useful to you and is fun to you, God will give it to you. If something you ask in prayer is not good for you, God who loves you will not give it to you even if you ask for it 842 times.
Would you let your 4-year-old child jump into the deep ocean because they would like to do so and always ask for it? No, you would not allow that because of your loving care and the health of your child. It’s no different with God, your loving Heavenly Father. Something that is not good for you, God will not give you, no matter how long your prayer is.
That is why it is very important that we always tell God that His will, and not our will, will happen, because we can rely on it that His will is always better for us than what we imagine.
“And when you pray, do not keep on babbling like pagans, for they think they will be heard because of their many words.” (Matthew 6:7; NIV)
Ask God for guidance and helpful knowledge when you are unsure. “If any of you lacks wisdom, you should ask God, who gives generously to all without finding fault, and it will be given to you.” (James 1:5; NIV)