You need to take the context of this scripture also.
Luke 6V46:"And why call ye me, Lord, Lord, and DO NOT the things which I say?
V247:"Whosoever cometh to me, and heareth my sayings, and DOETH them, I will show you to who he is like.
V48:"HE is like a man which built a house, and digged deep, and laid the foundation on a rock: and when the flood arose, the stream beat vehemently upon that house, and could not shake it: for it was founded upon a rock.
V49:"But he that heareth, and doeth not, is like a man that without a foundation built a house upon the earth; against which the stream did beat vehemently, and immediately it fell; and the ruin of that house was great."
Bottom line, one whose actions back up their faith, is different to one who profess God, but when the test of their faith comes, they CHOKE.
The fact that someone says "Jesus is Lord" by the Holy Spirit, DOES NOT in any way, shape or form prevent them from choosing evil over good.
Judas was hand picked by Jesus and yet he never called Jesus Lord, in the right sense of your scripture's context of the Holy Spirit.
Matthew 16V17:Peter called Jesus Lord and Jesus commended him the same quote you gave, however, Jesus rebuked Peter not to long after, when Jesus told him, that the devil was using him, when Peter objected and pledged to fight for Jesus -- and not allow Jesus to go to the cross.
Human God given Free Will is not over ridden by the Holy Spirit, and we have to continue being in the Holy Spirit, which is not a one time thing--but a continuous abiding in the Word of God, which cleanses us all through our life time as believers.
EDIT: This is food for thought and a good question.
Since there are lots of people who think, that they are automatically going to see the pearly gates, by one confession of faith, without living every day in the Holy Spirit and in the cleansing power of the Word of God.