"When you pray, you are not to be like the hypocrites; for they love to stand and pray in the synagogues and on the street corners so that they may be seen by men. Truly I say to you, they have their reward in full. But you, when you pray, go into your inner room, close your door and pray to your Father who is in secret, and your Father who sees what is done in secret will reward you. And when you are praying, do not use meaningless repetition as the Gentiles do, for they suppose that they will be heard for their many words.” (Matthew 6:5-7)
NOTE: rewarded does not mean we always get what we ask for, but rewarded for going to God privately with our prayers rather than depending on the prayers of others. I think Paul prayed the following prayer for his friends in his "inner room" which he then put into a letter to them what he had prayed for them...
"...that He would grant you, according to the riches of His glory, to be strengthened with power through His Spirit in the inner man, so that Christ may dwell in your hearts through faith; and that you, being rooted and grounded in love, may be able to comprehend with all the saints what is the breadth and length and height and depth, and to know the love of Christ which surpasses knowledge, that you may be filled up to all the fullness of God." (Ephesians 3:14-19)
Here are some other simple prayers that are recorded in the Bible…
“Father forgive them…” (Luke 23:34)
“God, be merciful to me, the sinner.” (Luke 18:13)
“Father forgive them…” (Luke 23:34)
“God, be merciful to me, the sinner.” (Luke 18:13)
“Come swiftly, Lord Jesus.” (Revelation 22:21)