Answer: We should be filled with inexpressible and glorious joy, because we are receiving the goal of our faith, the salvation of our souls, (verses 8 and 9).
MORE INFORMATION AND/OR OTHER SCRIPTURE REFERENCES:
"Inexpressible" joy, or "unspeakable" joy is from the Greek verb which literally means "not + to speak out." It means that there are just no words to describe this kind of joy!! This is what Paul called the "indescribable" gift in 2 Corinthians 9:15: "Thanks be to God for His indescribable gift!"
"Glorious" joy is a "glorified joy," like the glorified face of Moses in Exodus 34:29 (being translated "radiant") and in 2 Corinthians 3:10, where it says: "For what was glorious has no glory now in comparison with the surpassing glory."
The above describes what we should be filled with, because we are NOW and in eternity receiving the goal of our faith, the salvation of our souls:
2 Corinthians 5:6-10: "Therefore we are always confident and know that as long as we are at home in the body we are away from the Lord. We live by faith, not by sight. We are confident, I say, and would prefer to be away from the body and at home with the Lord. So we make it our goal to please Him, whether we are at home in the body or away from it. For we must all appear before the judgment seat of Christ, that each one may receive what is due him for the things done while in the body, whether good or bad."
Galatians 3:1-5: "You foolish Galatians! Who has bewitched you? Before your very eyes Jesus Christ was clearly portrayed as crucified. I would like to learn just one thing from you: Did you receive the Spirit by observing the law, or by believing what you heard? Are you so foolish? After beginning with the Spirit, are you now trying to attain your goal by human effort? Have you suffered so much for nothing--if it really was for nothing? Does God give you His Spirit and work miracles among you because you observe the law, or because you believe what you heard?"
Philippians 3:14: "I press on toward the goal to win the prize for which God has called me heavenward in Christ Jesus."
1 Thessalonians 5:8-11: "But since we belong to the day, let us be self-controlled, putting on faith and love as a breastplate, and the hope of salvation as a helmet. For God did not appoint us to suffer wrath but to receive salvation through our Lord Jesus Christ. He died for us so that, whether we are awake or asleep, we may live together with Him. Therefore encourage one another and build each other up, just as in fact you are doing."
2 Timothy 3:14-15: "But as for you, continue in what you have learned and have become convinced of, because you know those from whom you learned it, and how from infancy you have known the holy Scriptures, which are able to make you wise for salvation through faith in Christ Jesus."
