1 Corinthians 11 : 27 Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord. 28 But let a man examine himself, and so let him eat of that bread, and drink of that cup. 29 For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord’s body.

Now Paul enlightens the people on what they were doing could be wrong. To partake o f this ordinance lightly or still clinging to some sin in your life means you are saying what Jesus did for us is null and void.  He goes on to say we must examine ourselves thoroughly and make sure our hearts are right with God before we partake of the bread and drink of the cup. Finally he reminds us that if one eats of the bread and drinks of the cup unworthily. or really just not  believing in what the communion stands for  is mocking the communion.  This is basically saying one does not believe Jesus sacrificed Himself for us and this person is bringing damnation on themselves.  We just always need to remember to try to keep our life straight all the time but make sure we are right with the Lord if we are going to participate in taking communion.