It was revealed to them that they were not serving themselves but you, when they spoke of the things that have now been told you by those who have preached the gospel to you by the Holy Spirit sent from heaven. Even angels long to look into these things.
According to this verse, the prophets knew that the were serving someone else when they were writing about the coming Messiah. We are still being served by them and by those who have told us this wonderful good news.
That last little phrase can give you a glimpse of the grandeur of this message, of this story. I think as people we most of the time miss the big picture. I heard a pastor one time say, "...the salvation story has way more to do with the relationship between the Father and the Son than it has to do with us..." And I believe that.
It is all about Christ, and Christ makes it all about the Father.
If you are making your salvation about you, stop. Turn your eyes upon Christ. Focus on Him.