Make the Bible your prayer book. It is inspired of the Holy Spirit. The promises are sure to you as a believer. Your confidence and faith is strengthened when you ask according to God's promises. He hears and answers "Yes." Those who receive, ask according to God's word and will. That's asking God and receiving.
Praying is asking and receiving. When you ask God according to His word of promise, you are asking according to the will of God. This means you are certain of God's will. "Now this is the confidence that we have in Him, that if we ask anything according to His will, He hears us" (1 John 5:14).
You may believe God can do anything, but will He do what you are asking? It's certain He will, if it's according to His word of promise. The word of God is the will of God. "For all the promises of God in Him are Yes, and in Him Amen, to the glory of God through us" (2 Corinthians 1:20).
You can pray with confidence, according to God's word in the Bible. His answer will be Yes and Amen in Christ. You may be reluctant to ask God for anything because you think He may say no to you. His Yes is in His word when you ask in Jesus name. Jesus Christ is the Amen to your requests. Amen means "so be it." That's when the Bible is your prayer book.