There is a specific point in time when salvation occurs-the point when regeneration takes place. The issue for people is to know if they now really trust in the person and work of Christ. People often lack assurance because they question the procedure they went through when they accepted Christ. Many evangelists and preachers emphasize the need for some form of public confession of faith like going forward at the end of a service or raising your hand. If people receive Christ privately, they may wonder if they should have made a public confession or prayed a different prayer.
People often lack assurance because of struggles they have with certain sins.
They wonder if a true believer would have these kinds of problems. The real problem is ignorance of man's sinful nature, the spiritual warfare we are in, God's means of deliverance, and the need to grow and mature in Christ. The primary reason behind a lack of assurance is doctrinal misunderstanding and the consequent lack of faith in the finished work of Christ. This means a failure to understand the Word and its teaching regarding mankind, his sin and inability to work for or maintain his salvation, God's perfect holiness, and the finished nature and sufficiency of the work of Christ. Finally, people often lack assurance because they have erroneously been taught that they should look to themselves and their works as the primary proof of their salvation.