This is a question that has been pondered over and over again in the bible.

True faith is confirmed by visible evidence and fruit in your life (though salvation is by faith alone, not by these works). The book of 1 John provides key practical tests for assurance:

• Obedience: A genuine desire to follow God’s commands and turn away from habitual sin (1 John 2:3-6).
• Love for believers: Authentic love for other Christians (1 John 3:14).
• Correct belief: Holding the right view of Jesus as the divine Son of God who came in the flesh (1 John 4:2-3, 5:1).
• Holy Spirit’s inner witness: The Spirit’s testimony that you are God’s child, along with growing conviction of sin, comfort, and hunger for holiness (1 John 4:13; Romans 8:15-16).

You won’t be perfect (1 John 1:8-9), but there should be a real changed life, hatred of sin that so easily beset us, and ongoing growth in godliness (2 Corinthians 5:17). These are signs that your faith is authentic.