Being a new Christian is like a toddler learning to walk

Being Born Again Is Instanteous - Justification

Being born again is instantaneous. It happens when we confess our sins,  ask God to forgive us and fill us with the life of Christ by his Holy Spirit. This is called JUSTIFICATION BY FAITH, because I am put right with God (justified) through the Blood of Jesus shed on the Cross for my sins and God sees me just as if I'd never sinned.

Growing More Like Christ Takes A Lifetime - Sanctification

Growing more like Christ on the other hand takes a lifetime.  HEBREWS 5:11-6:3; 1 JOHN 2:12-14 outline the process of growing up as a Christian, which is called SANCTIFICATION (from the Latin word sanctus = holy/set apart for God.) There are several stages -

Stage 1: The Baby Stage (Greek brephos; nepios = infant, baby)

A baby can only take milk, not solid food; is totally dependant on others for everything; and is totally self-centred.   1 PETER 2:2; 1 CORINTHIANS 3:1-3

Stage 2: Little Children/Toddlers (Greek teknia; paidia = infants/little ones)
1 JOHN 2:12-13

Young Christians focus on Father God and his forgiveness of their sins. It's a wonderful relief to come to know God as my loving heavenly Father and that my sins were forgiven the moment I put my trust in Jesus Christ's death on the cross to take the punishment my sins deserved.

Stage 3: Adolescence/Young manhood (Greek neaniskoi = young men)
1 JOHN 2:13-14

The emphasis here is on action, victory over sin and spiritual warfare. Adolescence is typically a time when young folk are looking for action!

They can be the most enthusiastic Christians around and not afraid to wage spiritual warfare, although sometimes they lack the wisdom that comes with maturity. It's also a time when they can become frustrated with older Christians and things like older styles of worship and music.

Stage 4: Spiritual Parents (Greek pateres-fathers)   1 JOHN 2:13-14

The emphasis here is on our personal relationship with God as heavenly Father and becoming spiritual parents ourselves to young Christians. This is the stage when disciples also become disciplers.

Postscript

In the unit headed HOW CAN I BE SURE we saw that Auguste Comte claimed to have discovered a law underlying all the sciences.

According to this law of human evolution, mankind's thinking has evolved from an infantile religious phase through a metaphysical phase to a mature scientific phase based on a scientific process of observation and evidence-gathering.

It is interesting to note that Comte's so-called 'law' is the very opposite of the way we grow to spiritual maturity as Christians.