100% Assurance of Christian Doctrines

Actually I don't know in a flesh point of view whether the doctrines I follow are 100% true unless I allow the Holy Spirit to convict my heart to follow certain doctrines. I am 47 years old, I have learned so much about doctrines because I have been going to churches since I was an infant. I didn't actually become a Christian until I accept Christ as my lord and savior as a teen. Like David's experiences, God meets us in our heart rather than our mind therefore we need to focus on the "heart of the matter". Every wrong act or practice begins with a "thought". Even though, our actions may "appear to be right" but we need to understand that Christians are always engaged in a spiritual warfare. Proverbs 4:23, it says "Above all else, guard your heart, for it affects everything you do." Spiritual maturity requires great care and a true knowledge of ourselves to distinguish a spiritual burden from irritation around us but at the same time, we cannot close our minds to everything that is happening around us. "Be very careful, then, how you live--not as unwise but as wise, making the most of every opportunity, because the days are evil." (Ephesians 5:15-16). We are to worship God from our hearts because we are the temple of the living God (2 Corinthians 6:16), that God will search us and try us, and know our thoughts.(Psalm 139:23). Our Christian practice (life) starts in our hearts. Our thoughts are the product of our thinking and it is not our thinking that shapes our character, but the Holy Spirit that leads our thoughts and shapes our character. A person who have the Holy Spirit in the heart will understand God's standards of "sin" because a Christian will understand God's holiness. A person without having the Holy Spirit in the heart will not understand God's holiness therefore a person will define God's definition of sin in a human point of view (rather than spirit). Salvation is free through Grace (undeserve kindness) of God and His unconditional love. Is God's grace cheap? Becoming a disciple, following Jesus Christ requires personal cost, giving up your selfish "me" and become like Christ. Love is NOT conditional however discipleship is conditional. Jesus might have grieved over His Cost of Discipleship requirements, but He never ran after them to try to win them with rosy promises. Christians all around us are trying every shortcut they can think of, to get "something for nothing" in the kingdom of God. Although God's grace has been given freely to humans who do not deserve it, the grace of God and point out that Jesus commanded us to take up our cross and follow Him. Our minds are so much set on things earthly and so little on things above. To grow in Christ as God desires demands on our submission to Him. The Holy Spirit gave me assurance of my faith and doctrines I follow. No Church, No Denomination, No pastors or anyone can do this for me. Holy Spirit is the ONLY person who can do this.