This call to examine yourself, a call for self-examination of your spiritual state, is one that is critically important for all of us to be sure that we are on the narrow pathway to eternal life in heaven .
A person is justified (made acceptable to God) by the free gift of having our sins wiped away by believing in the sacrificial death and resurrection of Jesus . Through this belief, the person is seen by God as being righteous (in right standing with God). However, the true belief to receive this gift of God must be far more than just words spoken or thoughts in our mind.
A person's belief must be sourced from the heart where there is a recognition of what sin is and a commitment to turn from it and follow Christ Jesus. The difference between the person just believing with their mind and the one who believes in their heart is obedience.
The evidence of a person's belief is living a new life of daily surrender to God. A daily life of setting aside their own will and allowing Jesus to be Lord of their life, becoming increasingly like Christ Jesus. A life of desire to increasingly know, love and obey God and to live a daily life which glorifies and honors Him.
2 Corinthians 13 vs 5
Examine yourselves as to whether you are in the faith. Test yourselves. Do you not know yourselves, that Jesus Christ is in you?—unless indeed you are disqualified.