Complex sentence: In the mind of a narcissist there is poorly defined boundary between Self and others and others who meet their needs and those who provide gratification may be treated as if they are part of the narcissist and should live up to their expectations.
Split into simpler sentences: In the mind of a narcissist, there can be poorly defined boundary between Self and others. Others who meet their needs and those who provide gratification may be treated as if they are part of the narcissist and expected to live up to their expectations.