There is nothing crazy, ridiculous, or unreasonable about one person talking to another person. Prayer is simply conversation with our Creator. God is spirit, but He is also a Person, which means He has personality, with feelings, desires, and intelligence. He enjoys interaction with His creation, and when we choose to seek Him, He promises we will find Him (Jeremiah 29:13). The Bible is filled with conversations between God and people, beginning in the Garden of Eden (Genesis 2:17). God created man for fellowship, and conversation is a big part of that. He delights in us and wants us to delight in Him (Psalm 37:4, 23).
God Himself invites us to call on Him, and He promises to answer (Jeremiah 29:12; Psalm 50:15; Ephesians 6:18; 1 John 5:14). Jesus taught us how to pray in what has become known as "The Lord’s Prayer" (Luke 11:2-4). His own prayer, recorded in John 17, is also a good example of heartfelt, intimate prayer between the Father and the Son. If we have become children of God through faith in Jesus Christ, we can pray just as intimately and know that our Father hears us (John 1:12).
There are too many instances to cite of perfectly sane people talking to God. Some of the most noteworthy are Moses (Exodus 4:10), Elijah (James 5:17), David (2 Samuel 24:10), and Jesus (Matthew 11:24; John 17:1). Many great leaders of the past have relied on prayer to make their decisions. George Washington, Abraham Lincoln, and most of America’s Founding Fathers believed strongly in the power of prayer. Great scientists such as Isaac Newton, Louis Pasteur, Francis Bacon, George Washington Carver, and Galileo also believed in prayer. None of these people could be classified as "insane."
Those who walk closely with God also hear His voice speaking to them. God’s voice is rarely audible. He speaks into the heart of a person who is wholly committed to Him (Acts 8:29; 10:19; 2 Corinthians 12:9). He speaks through His Holy Spirit into the hearts of His children to guide, protect, and encourage them (Romans 8:14; Galatians 5:18). Jesus said, "My sheep know my voice" (John 10:27).
When we place our faith in Jesus Christ for salvation, God’s Holy Spirit comes to live inside our hearts (1 Corinthians 6:9). He helps us pray in a way that communicates our real heart’s desire to God (Romans 8:26). In John 14:26, Jesus told His disciples, "The Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you." Often, God’s answer to our prayers is already found in His Word. As we pray, the Holy Spirit brings His Word to mind, and we have our answer. Human beings never become all they were created to be until they learn to communicate with their Creator.