You know that saying - "Nobody is happy when mama is NOT happy"?  I believe we can take that one to another level, the highest level.  Things are just not right and there is no happiness or joy around when your relationship with God is either not in existence or going through some "bumps" or challenges.  If you have a personal relationship with God through Jesus Christ His Son and you are reading His Word on a daily basis, speaking to the Holy Spirit everyday (including Him in on everything) and allowing Him to lead, guide, and direct you...then it is very possible you have experienced The Joy of the Lord. 

When believers are in God's will, when we are in sync with His plan for our lives - His joy can be a physically manifested experience (I know, I've been there).  To me it is the kind of happiness and joyful emotion that comes when my own earthly Father or Mother tells me - "I'm proud of you son.  You are doing really well.  However, we will always love and support you, no matter what."  I receive this kind of spiritual and emotional jolt/charge when I hear the Lord say through Nehemiah - "Do not grieve, for the joy of the Lord is your strength." (Nehemiah 8:10) 

The context of this verse shows the Israelites desiring to get back into God's Word and hear and see what it says, especially concerning their relationship with Yahweh.  Israel's past was not a good picture and they recognized that and grieved.  However, the Lord also saw that Israel was back studying The Word and coming back to Him and it seems He was pleased to the point where He had "joy" over Israel returning to the Word and told them "Do not grieve, for the joy of the Lord is your strength."  This "joy" and further studying of the Word turned into Feasts that were once forgotten.  Then national revival seemed to hit Israel as a result of this return to the Word and this outbreak of God's joy for His provisions and His Word. 

"All the people assembled as one man in the square before the Water Gate. They told Ezra the scribe to bring out the Book of the Law of Moses, which the LORD had commanded for Israel.  So on the first day of the seventh month Ezra the priest brought the Law before the assembly, which was made up of men and women and all who were able to understand.  He read it aloud from daybreak till noon as he faced the square before the Water Gate in the presence of the men, women and others who could understand. And all the people listened attentively to the Book of the Law.  
They read from the Book of the Law of God, making it clear and giving the meaning so that the people could understand what was being read.  Then Nehemiah the governor, Ezra the priest and scribe, and the Levites who were instructing the people said to them all, "This day is sacred to the LORD your God. Do not mourn or weep." For all the people had been weeping as they listened to the words of the Law.  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 8:1-3, 8-10)

When I cross-referenced Nehemiah 8:10, two other verses appeared that spoke to the "joy of the Lord" or rejoicing in the Lord - Deut. 12:18 and 16:11.

Deuteronomy 12:18 says, "and you are to rejoice before the LORD your God in everything you put your hand to."  This becomes easier and easier as we keep the blessings and promises of the Lord in the forefront of our minds and spirits.  This is also easily accomplished the more believers are in His Word and can see, read, and quote out loud the Lord's blessings and promises to ourselves.

Deuteronomy 16:11 says, "And rejoice before the LORD your God at the place he will choose as a dwelling for his Name".  The place He chose as His dwelling for His name at this point was a physical, man made temple of wood and other supplies.  God's temple, in this day, is the believer's body (heart, mind, spirit).  How much more should we be able to receive the Lord's joy knowing He lives within us, by the power of His Holy Spirit, than back in the days of a wood and stone temple the Israelites built and worshiped at.

It seems the key in opening the door for more joy in the Lord is reading God's Word.  If you are not presently reading - start.  If you have paused, resume.  If you are reading, stay engaged.  Then watch His joy, His support, His "that a boy/girl!" - attitude, watch His unity with you make you laugh and cry at the same time, watch as because you have a relationship with God and are in sync with Him - The Joy of the Lord flows.