"The seventy-two returned with joy, saying, “Lord, even the demons are subject to us in your name!” And he said to them, “I saw Satan fall like lightning from heaven. Behold, I have given you authority to tread on serpents and scorpions, and over all the power of the enemy, and nothing shall hurt you. Nevertheless, do not rejoice in this, that the spirits are subject to you, but rejoice that your names are written in heaven.” Luke 10:17-20
BAM! OUCH! This is both an amazingly great and an incredibly important rebuke. The 72 return, happy that they have spiritual power Jesus, amazed at what they were able to do. How does Jesus respond? "Don't let the power go to your head. Don't miss what's important." I doesn't matter if you can heal 10,000 people. It doesn't matter if you cast out hundreds of demons. If you evangelized millions. If you changed the world for Jesus. Don't rejoice for yourself in any of these things, because this power and work was only given to you by God. Without Him you are nothing. Rather, rejoice that you are known by God. Rejoice that your name is in the book!
Nothing we do is worth anything compared to being known by God. This is what we rejoice in! Anything God gives on top of that is a small gift, because that gift is the greatest and most important. That gift, not our works in Jesus' name, are the source of our joy.