[You are the third person who asked the same question, first in English though. Here I give a slightly different answer.]
In this passage, Jesus gave Judas the Eucharist, the body, blood, soul and divinity of Himself. And it is said that with that Satan entered Judas. Obviously, Satan was not in the Eucharist.
When we receive the Eucharist, we are saying “yes” to be one with Christ, it presupposes a covenantal relationship with Jesus. It is an act of saying “yes” to die to myself, take up my cross, and follow Jesus unreservedly and whole-heartedly. I will nail my sin to the cross. I will rather die than to offend You Lord again.
It is for this reason that the Church always teaches that only one who is in the state of grace may receive Holy Communion; my life must correspond to my “yes” in receiving Holy Communion, that indeed my action corresponds to a life of commitment to Christ.
But if I have committed mortal sins, if my thoughts and desires are not to be one with Christ, St. Paul in 1 Cor 11 said that then by receiving Communion I will be receiving my own judgement. This is because I cannot be saying “yes” to be with Jesus in my action of taking Communion, but in actuality all along I have been saying “no” in my heart because of my refusal to be reconciled with Him. That is making a mockery of the Eucharist, making the Communion—Jesus Himself—a liar.
That’s what happened to Judas. He did not want to be in communion with Jesus. He took the Communion, and so ate his own judgement. So instead of benefiting from the salutary graces coming from the Eucharist, he hardened his heart and ran off to begin executing his plan of betrayal.
The same can be said of all of us, when we find ourselves in the state of sin but refusing to first go to confession before receiving Communion. We find ourselves all sorts of reasons: I did not have the time; it’s not a big deal; Jesus will forgive; people would wonder why I don’t receive… Those are the voices of Satan, already standing at the door ready to come into our heart. Do not blaspheme the Eucharist. Go to confession first. And if you did not have the opportunity before mass, abstain from Communion and go confess as soon as possible. This act of virtue is greatly pleasing to the Lord, and your resolve will gain you many graces for resisting the devil and a deeper love for the Eucharistic Lord.