The first three words of the Nicene Creed in English are: "I believe in..." Only one word in Greek -- "Pisteuo"; two in Latin: "Credo in..."
Not just "I believe" -- like "I believe 2 + 2 = 4" or "I believe the sun will rise in the East tomorrow" -- Greek would use "Theoristeo" or "Pestho" for mere intellectual belief.
Instead, we have the word for "visceral belief", "passionate belief" -- a belief that commits one to changing one's life and habits. The older (by 150 or so years) Apostles' Creed, which scholars think was alate 1st or early 2nd Century Roman "Baptismal Symbolon" (Great & Holy Oath, sworn at Baptism) also begins "Credo in . . ." in Latin.
By this Symbolon, this Baptismal Oath, we commit ourselves not merely to intellectual belief, but to real change of heart, change of life, change of behavior. And by our repetition of the Nicene Creed in the Eucharistic Liturgy (Holy Sacrifice of the Mass), we re-commit ourselves over and over again.
The New Testament word for this change is "metanoia", from the Greek roots "meta" ("another, beside, beyond") and "nous" ("mind"). This is often translated "repent" in English, but, while repentance is in there, it is all too often an intellectual exercise, rather than a will-full and heart-felt commitment to change. True metanoia is hard work, not just repeating a formula.
St. James (The Brother of the Lord) says in his Epistle: "Faith without good works is dead." And what better (or harder) work than to change oneself?
