Paul Washer is a powerful preacher and evangelist. He once had a seminary student send him a message. He was afraid that he was too bad to enter the ministry. He sent him a message that simply said, "I think I am too wicked to be in the ministry." And Paul Washer wrote him back and said, "You are right. In fact, you don't know how wicked you are."
The young man replied, "Thanks a lot."
And Washer replied, "Friend, your heart is for the Lord, and your life is lived in service to him. Your level of sanctification and commitment puts me to shame at times. But I am happy and you are not. Do you know why? Because I have chosen to trust in Christ, and you are still, in part, trying to trust in yourself."
Beloved, Washer was right.
The problem most people have with assurance of salvation is that they have not reached the place where they can stop trusting themselves and start trusting Christ.