You can call me what you want, as long as the Lord is still calling me that all that counts!:)
I would consider it a sin of pride to call myself a "saint."
Pride is the excessive love of one's own excellence. It is ordinarily accounted one of the seven capital sins. St. Thomas, however, endorsing the appreciation of St. Gregory, considers it the queen of all vices, and puts vainglory in its place as one of the deadly sins. In giving it this pre-eminence he takes it in a most formal and complete signification. He understands it to be that frame of mind in which a man, through the love of his own worth, aims to withdraw himself from subjection to Almighty God, and sets at naught the commands of superiors.