Can you be sure you are a Christian?

1 John 2:3-6 (CSB) ³ This is how we know that we know him: if we keep his commands. ⁴ The one who says, “I have come to know him,” and yet doesn’t keep his commands, is a liar, and the truth is not in him. ⁵ But whoever keeps his word, truly in him the love of God is made complete. This is how we know we are in him: ⁶ The one who says he remains in him should walk just as he walked.