Assurance comes when we put our trust in the Word of God. God said it, I believe it, that settles it forever! If nagging doubt persist, then memorize and ponder these promises. Think on these things!

And the witness is this, that God has given us eternal life, and this life is in His Son. He who has the Son has the life; he who does not have the Son of God does not have the life. These things I have written to you who believe in the name of the Son of God, in order that you may know that you have eternal life. 1 John 5:11-13 Truly, truly, I say to you, he who believes has eternal life. John 6:47 My sheep hear My voice, and I know them, and they follow Me; and I give eternal life to them, and they shall never perish; and no one shall snatch them out of My hand. My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of the Father's hand. John 10:27-29 Truly, truly, I say to you, he who hears My word, and believes Him who sent Me, has eternal life, and does not come into judgment, but has passed out of death into life. John 5:24