The separation of self and other is our fundamental illusion. This is the domain of the ego. If we understand that we are all part of the same entity, then there is no room for ego. The ego roots for the self over the other. The ego feels that the bad things that befall us are tragic and the bad things that happen to others are merely unfortunate (or perhaps, even deserved). The ego may turn on the self and feel that the tragedies that we experience are due to a personal deficit, character flaw, or curse. These are destructive feelings and lead us to pain and suffering.
If we think of ourselves as something other than our mortal bodies, we can use that sense of separation to see through the ego. We will see our experiences as though they are happening to others. We won’t take things so personally.
Conversely, if we think of others as ourselves, then we root for them, take pride in their accomplishments, and we suffer their losses. There is no room for jealousy. In this approach our ego becomes communal and does not inspire us to spread pain.
Using our inclination to divide the world into self and other, we can separate our Self from our ego, making Ego the other, whom we can blame for our suffering. As we sit in meditation, we can watch all of these ideas of separation dissolve. We can own our ego and love ourselves.