When you are joyful, how can you have desires? And how can you be joyful right now when you have desires? Desire appears to lead you to happiness. In fact, it cannot. And that is why it is maya.
Maya means that which can be measured. The word ‘measure’comes from the word Maya. All that can be measured on this planet is Maya.
Maya means illusion. Maya means that which is temporary, that which is not the truth. Maya simply means appearance. Like the sunset is maya, because it only appears to be setting. In reality it is not setting. So sunset is maya.
That which changes, which is not constant, which does not appeal, is Maya. That which changes every moment and that which you can measure is Maya. That which you cannot measure, which does not change is truth.
One who is familiar with the real stuff, to him even the fake thing seems real. And to the one who is familiar with the fake thing, even the real appears as fake. This is maya. What is real and what is unreal has to be found out. Therefore you need an inward eye (antar drishti). This is possible through yoga and meditation.