Do you fear anything? Do you know how to stop fearing? 1 John 4-5

1 John 4:18 (NASBStr)

There is no fear in love; but perfect love casts out fear, because fear involves punishment, and the one who fears is not perfected in love.

We have in the verse above an in-depth statement with many, many building blocks to further and establish our faith.   Theologically it follows John's thoughts on how love is an evidentiary result of having a true relationship with God.   Word Biblical Commentary states it this way:

By now, John has described three necessary marks of the authentic Christian:possession of the Spirit (v 13); confession of Jesus as God's Son (v 15); and living in love (v 16).

We see, from John's argument, that faith, trust and love all play a large part in our relationship with God.   In the development of his argument, John is not showing how that relationship with God affects us in regard to our relationship with other believers (we should necessarily love them) and with our view of the future.  Since both the Gentile and Hebrew world had some concept of judgement, John wants both to know that there is no reason to fear future judgment, or any judgment, because perfect love (the love God has for us) transcends fear.   Again, Word Biblical Commentary:

The train of thought which began in v 16 is thus completed. God is love; the person who lives in love remains in God, and God in him; in this mutual indwelling love finds its complete expression; and, as Jesus is imitated closely, the believer's last fears are banished (cf. Westcott, 158).

Fear is not a matter of self-confidence.  Fear is a matter of love ... the love God has for us.   His perfect love means he has taken care of all judgment and will continue to do so.   Fear is a matter of faith (Luke 8:25).   From a psychological point-of-view this his a key turth.   Psychologically we all fear something.  In our working with others when they tell us their fears (rejection, abandonment, loss, discovery, inadequacy, insignificance, approval, etc) they are telling us that they do not trust mankind, those in their lives, to love them despite these things, or something.   Because God loves us completely and fully, we have no reason to fear any of these things; which are actually poor judgments people are making about themselves our about us.   John tells us we can have confidence (1 John 4:17) and not fear because God's perfect love casts our - rids us of fear.   Fear is a form of punishment.  Since Jesus defeated sin, fear no longer has control over us.  When we come to faith that God fully loves us we can rest in that love and not worry if anyone likes us, supports us, believes in us, we are adequate for them, they will leave us lonely, etc.   God fully loves us and that casts out fear.  If we fear the answer is to come to full faith that God indeed loves us in a perfect way. If we understand that than we understand that no matter what happens to us is in God plan for us.  And, in His plan He is simply expressing His perfect love for us.