Joy makes us strong?

"Celebration brings joy into life, and joy makes us strong."  pg 191

Scripture tells us that the joy of the Lord IS our strength (Neh. 8:10)  IS our strength, IS our strength.  One week into the lent season I have been meditating on this "IS".  IS our strength? What does that mean?  How can the Lords Joy be my strength?  John records Jesus saying in John 15:11 "I have told you these things so that my joy may be in you and that your joy may be made full."  Is this another way of Jesus saying, "I told these things to you so that my JOY may be in you and my JOY will make you strong!"
The Lords Joy=strength.  We know that only obedience produces pure joy (Luke 11:27-28) And Jesus is telling us in the John scripture that we cannot produce joy because we are incapable of obedience without His spirit. (John 15) We are but branches that apart from the vine can produce nothing! So here is my final equation.....

Jesus' obedience to the cross = PURE JOY
Jesus gives His Spirit to us = Jesus' obedience to the cross now lives in us.
Submission to His Spirit in us leads us to a cross = His PURE JOY in us.
Natural response = A life of celebration in response to Jesus' obedience to the cross!

Now that is my kind of math!

-Reid