This is a covenant meal. This means that the covenant features of blessing and cursing run right through the middle of it. In this covenant, God demands what He has always demanded from covenant-keepers, and that is faith in the only one who was a covenant-keeper completely, that is, the Lord Jesus. That is it—simple faith. Trust Him, rest in Him, come to Him, and feast in Him. He is the epitome of true humanity, and as You look to Him in faith, you are being built up into that perfect humanity.
The only alternative to this faith is unbelief. But we must be careful here, because an over-active and pious conscience has made us think that unbelief is any kind of failing, at any level. No, unbelief is rejection, not imperfection in your acceptance.
We are people of faith, we have faith. Do we have faith perfectly? Is our faith not to be improved upon? Are there sins and faults mixed in with this genuine faith? Of course, just as when you are learning to play the piano, you make mistakes. But even when you make mistakes, you are always playing the piano and not, say, the tuba. Such mistakes are not a disqualification for coming to the Supper—they are the precise reason why you must come.
Unbelief that disqualifies is persistent, hard-hearted, obstinate, willful, and this is the most important point about it, obvious to the whole world.
So do not spend your time researching your motives over the course of this last week to determine if you are fit to come. Any baptized person who is concerned over their fitness to come is, by definition, commanded to come. We cannot be reminded too often. This meal is not your reward for being good. It is God’s nourishment for those who would be good. It is God’s kindness for those who would grow up into Jesus Christ. So, come, and eat. Come, and drink. You are in Jesus Christ, and this is why you are welcome.