From: Hava Nagila (documentary)
The niggun is a song without words because, ultimately speaking, to reach God no words will suffice. And it's done through the universal language which, in Hasidic Judaism, is music. There are ten levels of prayer and above them is music. But there ain't no happy in it that is not connected with a little, bitter after-taste. Life is beautiful. Isn't it sweet, isn't it awesome; I'm going to die tomorrow.
It's this wonderful tension between aspiration and reality. In my dreams you don't even know how high I can go. The reality is that I'm going to be heartbroken thoroughly and completely right here on this earth. And a beautiful niggun manages to trace that distance.
One of the main principles that governs Hasidism was not only can you serve God with joy but if you're bummed out you can't serve God. So Hasidism is resolute, monomaniacal, about saying that you have to find a way to access the joy that you have. Joy brings you close to God.