How do you come to Mass? I do not mean, do you drive or walk. I mean what is your attitude? The way in which we approach the celebration of the Mass will determine how well we benefit from it. This may sound odd to modern American ears, but we should never come into the Mass as an "I"; we should always come as one of "us". When we become individualistic in our approach, we will definitely miss the main points of the Mass--which is to humble us enough to teach us how to trust in God.
If we approach as an "I" it is like we are entering a "group private devotion". We do not come into the Mass to sit alone and ignore everyone else, just seeking to get something for self. That is what most people do in a movie theater; "I'm hear to watch, leave me alone". Yet, we are not supposed to be entertained in the Mass (yes, I already know that a large percentage of Catholics are abused with entertainment Masses).
When we come into church to participate in the Mass, we come to join in an event that involves many more people (and creatures, cf. Revelation chapters 4 and 5) than we can see in the building with us. We come to join with the body of all God's people who have lived down through history. We come to participate in worship that is already going on in Heaven. We come to do our part in showing the glory of our Triune God. When we do this, and only when we do this, we can leave having gotten something out of the Mass for ourselves.