Read this from Martin Luther this morning:

I will not call myself holy for what I have done nor be called holy by anyone else or praised for my sanctity.  I am holy because I can say with firm faith and pure conscience: Although I am a poor sinner, yet Christ is holy in His Baptism, Word, Sacrament, and the Holy Spirit.  That is the one true holiness given us by God.

But how do I attain it? Or what have I to do with the Holy Spirit?  Answer: The Holy Spirit has baptized me and preached the Gospel of Christ to me and enlivened my heart to believe.  Baptism does not spring from me, nor did faith and the Gospel, but He gave them to me.  For the fingers which baptized me were not the fingers of man but of the Holy Spirit.  And the preacher’s mouth and words which I heard were not the preacher’s own, but the words and preaching of the Holy Spirit, who gives inward faith, through such outward means, leading to sanctification.

Therefore, we should as little deny or doubt that we are holy than we are baptized and are Christians.