The Roman Emperor Nero was one of the greatest persecutors of Christians who ever lived. The letters of 1 and 2 Peter were written in that historical setting as a call to holiness under suffering.
John expounds holiness as something we both have already - given to us by God - and yet something we also have to work towards. Holiness refers to the character of a parent handed down to adopted children and also to the “Old Covenant “ with its detailed laws which set apart God’s people from those who were not his followers.
An emphasis on speaking the Word of God to ourselves, from scripture, is shown as the basis of what we post-moderns call “Cognitive Behavioural Therapy” - changing our actions by changing our thinking/attitudes.