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.

1 John 5:12 Whoever has the Son has life; whoever does not have the Son of God does not have life.

2 Corinthians 13:5 Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?—unless indeed you fail to meet the test!

Self reflections often reveal the selfish side because discovering we have the Son is not instant but rather a journey where He reveals Himself line by line and precept by precept. 

Isaiah 28:13 And the word of the Lord will be to them precept upon precept, precept upon precept, line upon line, line upon line, here a little, there a little, that they may go, and fall backward, and be broken, and snared, and taken.

At what point do we discover that being taken means we were chosen?

At what point does insecurity give birth to security in the believer?

May I say it is very likely that each of us have our own tipping point!