In him you also were sealed with the promised Holy Spirit when you heard the word of truth, the gospel of your salvation, and when you believed. The Holy Spirit is the down payment of our inheritance, until the redemption of the possession, to the praise of his glory. (Ephesians 1:13-14)

“My sheep hear my voice, I know them, and they follow me. I give them eternal life, and they will never perish. No one will snatch them out of my hand. My Father, who has given them to me, is greater than all. No one is able to snatch them out of the Father’s hand. I and the Father are one.” (John 10:27-30)

…you received the Spirit of adoption… Romans 8:15
For he chose us… Ephesians 1:4
…[Jesus came] so that we might receive adoption… Galatians 4:5

You can’t lose your salvation, but you can miss out on sanctification.

Therefore, my dear friends, just as you have always obeyed, so now, not only in my presence but even more in my absence, work out your own salvation with fear and trembling. For it is God who is working in you both to will and to work according to his good purpose. (Philippians 2:12-13)