Actually my question is similar to @ale901809.
Could you say the same with, "Ti credi."? It's my understanding that if the pronoun matches the verb conjugation, it makes the pronoun reflexive.
Mi credo = I believe in myself. Ah, wait. I see. It would be, I believe myself.
So, "Ti credi" would mean You believe yourself. Need the proposition. Got it. Nevermind. LOL