As I wrote on the blog finallyfree.org, in a post entitled "Nothing But Him":
There's nothing but G-d. He is the only true existence. We exist only in Him.
Do you know when it is that I start to want a drink?
When I start to feel like my own existence.
This whole idea comes from the verse in Deutoronmy (4:35), "There is nothing else besides Him" and its Chasidic explanations.
Anyway, an image I use to work on ingraining this concept is one that I found in a book of meditations by Gutman Locks called "There is One." Here it is:
Consider: When the water lies still and the sunlight rests upon it, a single globe will reflect from the water. But when the wind stirs the water, making waves, the sun's light will bounce off the water, forming a thousand reflections. Each reflection seems to be saying, "I am an individual reflection. I am here in my own location, and I am my own shape, while you, over there, are another reflection, not in the same place as I am, and not the same size as I am." And so it is with each of the myriad of reflections, each attesting to its individuality and its separateness. When these reflections are viewed upon the water, there appears to the mind to be a thousand lights, but when the eye is lifted up from the agitated water onto the smooth sky, it is seen that there is but one. A single sun is laying its glorious light upon an agitated body of water. Even after the light touches the water, it still remains a single light. It is only because the water is agitated that the reflection seems to break up and form into many lights, but in actuality, there is always just a single light. And so it is with us. Although we appear with good reason to be many, we are in fact, one.