The following quote is from 'Heart Advice, Weekly Quotes From Pema Chodron' :
OUR MISTAKEN FEELING OF SEPARATENESS
"At the level of absolute truth, there is no reason to suffer.
But at the relative level, we're all in considerable pain.
The cause of our discontent is our mistaken feeling of separateness.
This isn't based on anything tangible.
It's based on beliefs and concepts.
The duality of subject and object, self and other,
is an illusion imputed by the mind.
This absolute understanding is arrived at through the practice
of letting go.
Meanwhile, we can work at the level of everyday pain
and treat other people's suffering as our own."