"A human being is part of the whole, called by us 'Universe'; a part limited in time and space. He experiences himself, his thoughts and feelings as something separated from the rest: a kind of optical delusion of his consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and affection for a few persons nearest us. Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole nature in its beauty. Nobody is able to achieve this completely but striving for such achievement is, in itself, a part of the liberation and a foundation for inner security."
When you were a baby, you knew yourself to be a perfect, infinite expression of the Divine. Then along came the "terrible two's". You learned two things. How to say "no" and that it was no longer OK to let your body do whatever it wanted, in the moment. Love and approval was dangled as the carrot to persuade you to learn.
You were toilet trained, you learned to control your sphincters, and you learned to act differently from how you feel, in the moment. You learned that sometimes you have to put on a "social mask", smile when you feel like crying, be nice when you want to scream. You learned to speak, and you learned to lie with your words, your expressions and your actions.
Eventually, you forgot that the social mask you made, the role you were playing to get love and approval, is not who you really are. You forgot that you are really a perfect, infinite expression of the Divine. The mask blocked your awareness, and filtered your memories. It became a wall separating you from your own spirit. We call that wall "ego".
Ego is the "optical delusion" Einstein speaks of, in the quote above.
Ego is who you think you are. Any idea of yourself that is less than an expression of perfect, infinite Spirit. It is the barrier that blocks out the bliss of unconditional love you knew as a baby. That barrier is a construction you have been building your whole life. It is made of your lifetime's clutter of limiting beliefs about yourself, your fears, your emotional baggage of unreleased, unforgiven pain.
There are two parts of you, at odds with each other. The ego, that tries to create separation by judging, and the Spirit that only wants to love. Ego may say "There, but for the Grace of God, go I" and think itself compassionate, but it is really expressing a negative judgment about the other person, and congratulating itself on its superiority. Ego creates a separation out of fear, and is pleased not to be too close to another. Ego seeks to measure itself against other people and create hierarchies and beliefs of superiority and inferiority.
Spirit knows that Goddess, and that there is only one of us and it is All of us, with no part really being superior or inferior to any other part. Spirit knows that when you die and head for the Light, the only question that will be asked of you is "How well did you love?"
The process of Kundalini awakening and unfolding takes the ego barrier down again, brick by brick. It brings up a lot of old painful memories, so they can be forgiven, and it challenges every assumption you have ever made about who you are and what you are, and what you can do.
The useful stuff remains, like toilet training and language, talents and skills... but anything that is a barrier to you becoming a vessel of your own infinite soul, must be surrendered. All fears, all attachments and limiting beliefs.
Ego is very hard to see, when you are in it. "You cannot see the forest for the trees". However, by observing yourself it gets easier to discern what thoughts and impulses come from ego, and what comes from Spirit. That is called discernment. Next is learning to be grateful for the thoughts and impulses come from Spirit, and surrender the stuff of ego.
Discernment is a lifelong process. Even when you become self realized, you still must practice mindfulness, because if you attach to something then you can grow a new ego around it without noticing, and fall from grace.
In a way, discernment is simple: ego fears, and Spirit loves. Spirit looks for unity, commonality, and Ego looks for differences, separation.
So, to identify ego, look to see the fear that is expressed in thoughts, words, beliefs.
Sometimes this can be tricky, as ego is a stealthy bugger! Fear can hide in even the most selfless of ideals. "The road to hell is paved with good intentions." For example, hope is also fear of the future. Protection is fear of harm. Thinking someone needs help, can be a negative ego belief of their helplessness, not seeing them as able to take care of themselves. Like the parent who still sees their grown children as little and helpless. Ego sees illusion, creates illusion. Ego must step aside to make way for the bigger truth of Infinite Spirit.