We can end up in deep spiritual trouble. Spiritually hardened or diseased. Leave it long enough and it can actually lead to spiritual rot and death. Doesn't mean, of course, that we need to be squeaky clean before we come. No such thing as a squeaky clean person.
Communion is for sinners.
Sinners who know it. And who desire to see holy change come into their life. Who want to be distanced from their sin. Who want to be intimately connected to their Saviour. Sinners who want to have God's Spirit do healing, lifegiving, growing, restoring, beautifying work in their hearts.