First, we have confidence at the final judgment (2:28). Remaining in Christ will make the believer confident at the judgment when Christ appears.
John uses two different words for the Second Coming, judgment of Jesus. In the first case, he uses φανερόω, usually translated “appears.” In the Gospel of John the verb is regularly used for the incarnation In 1 John 1:2, the life “was manifest” (ESV); in 1 John 3:5, 8 Jesus “appeared to take away sin.”
In the second case, the word παρουσία (parousia) is a common word used for the second coming of the Lord. It is associated with the arrival and presence of a person (as opposed to absence). In the New Testament it most often refers to the Second Coming of Jesus as the Messiah. In 2 Thessalonians 2:8 Paul refers to the both the appearing (ἐπιφάνεια) and coming (παρουσία) of the Lord.
John is has in mind the second coming of the Messiah, when he judges the nations as he is establishing his kingdom This is different than the judgement seat of Christ (2 Cor 5:10), when the members of the church, the body of Christ stand before Christ to receive our reward.
If the believer is abiding in Christ, then they will have confidence when they face this future judgment before the Messiah. Confidence (παρρησία) is boldness to speak in a public venue. Luke used this word to describe the Gospel in the last verse of Acts, Paul continued to speak boldly and without hindrance (Acts 28:31). To “not shrink back” translates αἰσχύνω, to be ashamed. In early Greek the verb was associated with a hideous deformity or injury (Iliad 18.24, a disfigured face), but came to be used for anything that brought shame (or should bring shame, in the sense of “are you to ashamed to say this?)
John’s point here is we know we are a true child of God because we have that unusual confidence at the final judgment that we will be found worthy of eternal life based on the work of Jesus on the Cross.
Second, we practice righteousness (2:29). God defines righteousness (v. 29a) and the believer does that righteousness in daily life.
The verb is “doing” (ποιέω), a common word in 1 John. Once again John reflects the Jewish view that one “does righteousness” In Micah 6:8, for example, God has shown humanity what he wants: to act justly, or “do justice.” The noun (מִשְׁפָּט) is the common word in the Hebrew Bible for legal decisions. The judge is to render justice, make the correct decision. But more than this, to do justice is to treat all people right, so not giving favors to the wealthy or mistreating the poor.
In the context of 1 John doing righteousness begins with loving one’s brother and sister in Christ and not hating them (1 John 2:9-11). The one who is practicing righteousness has (already) been born of God (v. 29b).
The idea of being born of God is an important theme in the Gospel of John. For example, in John 3:3-8 Jesus explains that no one can enter the kingdom of God without first being “born again.” This causes some difficulty for Nicodemus who does not understand the metaphor. In John 1:13 those who believe in the Word are born, not of natural descent but from God.
The grammar is important, John says the one doing righteousness was born of God in the past and is still in the state of “born of God” at the present time (over interpreting the perfect tense verb here). In addition, the verb is passive, one does not birth themselves. We became the children of God when we accepted Jesus savior.
So a person does righteousness not to make themselves worthy to be children of God, but because they are the children of God. “A person’s righteousness is thus the evidence of his new birth, not the cause or condition of it” (Stott, Letters of John, 122).
This might be a different way of looking at righteousness. Righteousness is not the result of some pious ritual or spiritual discipline, but it is the natural result of being born of God. In essence, Christian ethics can be summarized as, “be what you are, a child of God.” And when we are living a life that pleases our Father in heaven, we will not lack confidence when he calls us into account at a future judgment.