@Cathode
Again, we are defining "biblical" differently. I use a stricter standard. I define "biblical" as "in the Bible".
Using your explanation of repentance, I see your explanation (that we are to repent, die to sin) as a biblical principle. But the practice you develop from that principle (the expression of that repentance) is not biblical (using "in the Bible").
Crossings yourself? Putting an ash cross on your forehead? I say - "Go for it". Express your faith. Live by biblical principles.
But I am cautious using "biblical" because once we say "this is biblical" it becomes prescriptive. One
should cross themselves or put ash on their foreheads, which is obviously wrong (it is the crime of the Pharisees).
It also can lead to evil. When we think of evil done in God's name four major organizations come to my mind - the Roman Catholic Church, Calvinists, Puritans, and the KKK.
The Roman Catholic Church used Scripture to oppress and persecute people. They used Scripture to gain wealth and build its organization. They identified this and reformed their organization.
Calvinists used Scripture to persecute non-Calvinists (particularly Baptists). They looked for a theocracy.
The Puritians probably sought out biblical principles more than any of the others mentioned, but the expression of the principles found were many times evil. They were a legalistic sect that persecuted not only other Christians but also members of their own sect.
The KKK used Scripture to support evil. They took what is biblical (God instructing His people to refrain from marrying pagans, to be a pure and holy nation) and misapplied biblical principles to create an evil ideology.
When we call our expressions of biblical principles themselves "biblical" we are trying to remove evaluation and examination.
That is my concern.