Can God say to you right now - "You are doing well, my good and faithful servant."?  If you can say, yes, to my question, then "the joy of the Lord is your strength".  It is His Joy that is being spoken of in Nehemiah 8:10.  Why would anyone receive strength in life from Him being joyous over them unless their relationship is right where He wants it to be?

Nehemiah said, "Go and enjoy choice food and sweet drinks, and send some to those who have nothing prepared. This day is sacred to our Lord. Do not grieve, for the joy of the LORD is your strength." - Nehemiah 8:10

In the development of the Christian, JOY is a wonderful benefit to grasp and never let go.  A definition of joy is "keen pleasure or delight".  So, the green phrase above could be read "the keen pleasure/delight of the LORD is your strength."  So, whenever you sense from God, His peace and joy - know that He has got you right where He wants you, He is delighted in you and you can derive Strength from that.

Ever wanted to throw a party because you finally - Got It!?  I have been there many times and will probably be there many more.  The people in Nehemiah 8:12 didn't just have joy, they had great joy "because they now understood the words that had been made known to them."  The Ah-Ha Moment, thanks to God, received some celebration.

"Then all the people went away to eat and drink, to send portions of food and to celebrate with great joy, because they now understood the words that had been made known to them." - Nehemiah 8:12

Another definition of Joy is great delight or great happiness. In the following verse (Nehemiah 12:43) we can see that great sacrifices were offered because God gave great joy to the people. Great joy, therefore, could be translated as at least one level above happiness. Their joy was so great that it manifested into a sound of rejoicing within Jerusalem that "could be heard far away".

And on that day they offered great sacrifices, rejoicing because God had given them great joy. The women and children also rejoiced. The sound of rejoicing in Jerusalem could be heard far away. - Nehemiah 12:43

Other Scriptures that speak to who and what Joy is for the Christian are.....

His presence is joy - Psalm 16:11.
His precepts give joy - Psalm 19:8.
His joy described as an anointing oil of joy (massaging oil of joy) - Psalm 45:7.
God's statutes are the heart's joy. - Psalm 119:111
Jerusalem considered "my highest joy". - Psalm 137:6
A wise son brings joy to his father, - Proverbs 10:1
The prospect of the righteous is joy - Proverbs 10:28
joy for those who promote peace. - Proverbs 12:20
A man finds joy in giving an apt reply-- and how good is a timely word! - Proverbs 15:23
A cheerful look brings joy to the heart, - Proverbs 15:30
When justice is done, it brings joy to the righteous - Proverbs 21:15
Perfume and incense bring joy to the heart, - Proverbs 27:9 (but in modest amounts)

Always consider the source.  If you sense you are being spiritually attacked or if you find yourself in a human situation that is devoid of joy - consider the source.  Then in the middle of your circumstance remember your source of Joy and the reasons for that Joy!

For example, let us examine one of my favorite stories of the Bible.  Shadrach, Meshach and Abednego were ordered to be thrown into a fiery furnace because they chose to obey God rather than an earthly king and worship only their God.  They were bound and then they said this - "O Nebuchadnezzar, we do not need to defend ourselves before you in this matter. If we are thrown into the blazing furnace, the God we serve is able to save us from it, and he will rescue us from your hand, O king. But even if he does not, we want you to know, O king, that we will not serve your gods or worship the image of gold you have set up." - Daniel 3:16-18 

Oh to have this kind of faith, this kind of confidence, this kind of peace, this kind of Joy in the face of death!

I say this because these three men survived the approach to the furnace!  The guards that held them and had to throw them into the furnace died in the process because of the intensity of the heat of the furnace (Daniel 3:22).  What?  What about Shadrach, Meshach, and Abednego you say?  "So Shadrach, Meshach and Abednego came out of the fire, and the satraps, prefects, governors and royal advisers crowded around them. They saw that the fire had not harmed their bodies, nor was a hair of their heads singed; their robes were not scorched, and there was no smell of fire on them." - Daniel 3:26-27

To know God as your source of everything, especially your joy is critical in life.  But look there's more!  Not only does God save you from the circumstances, like He did Shadrach, Meshach, and Abednego, He will incredibly influence others in the process and do a miracle in their lives as a result.  In this case, the king was influenced.  Observe what King Nebuchadnezzar proclaimed - "Then Nebuchadnezzar said, "Praise be to the God of Shadrach, Meshach and Abednego, who has sent his angel and rescued his servants! They trusted in him and defied the king's command and were willing to give up their lives rather than serve or worship any god except their own God. Therefore I decree that the people of any nation or language who say anything against the God of Shadrach, Meshach and Abednego be cut into pieces and their houses be turned into piles of rubble, for no other god can save in this way." Then the king promoted Shadrach, Meshach and Abednego in the province of Babylon." - Daniel 3:28-30

In the case of Paul and Silas being miraculously freed from prison, a guard's entire family was converted, other prisoners were influenced so mightily that they stay around, and the magistrate gave the word to let them go.  All this because Paul and Silas first knew God as their source of everything then they obeyed God (Acts 16:16-40).

I imagine there is nothing like experiencing a "Joy Robber" like being thrown in a furnace or locked in the very bottom of a prison in stocks and chains with multiple guard stations all the way to the top.  Both situations scream, "There is no escape!"  But, remember and draw from where your living water flows and whom you can count on no matter what comes your way.  Your joy and peace is in that dose of living water wherever you are in life.  What can anybody threaten the Believer with - Heaven? (nod to Pastor Dial)  Bring it on!

So, consider the source and draw from yours!