Two things are to be distinguished: salvation, and the knowledge of salvation. First, how am I to get saved? Then, how am I to know it?
First, my salvation depends solely and entirely upon the work and the person of Jesus Christ our Lord. Second, the knowledge that I am saved depends solely on the record, the word, the testimony of God. "He that believeth not God hath made Him a liar because he believeth not the record that God gave of His Son." 1 John 5:10.