Let's say one has spent the week preparing for communion, praying the prescribed canons and pre-communion prayers, fasting; and has gone to confession recently. Yet on Saturday night one gets into a fight with someone which is unresolved on Sunday morning. In this case one should probably not take Communion that morning, right?
I had a similar situation. I was very angry at someone when I went to church on Sunday. (oddly enough I can't remember now what I was angry about but it seemed really important at the time. Obviously there's a lesson to be learned there!) When I went to confession and confessed this, my priest asked me if I wanted to forgive the person. I replied that I was not ready to even think about forgiveness yet. So he informed me that I should refrain from receiving Communion.