From 'A New Earth' by Eckhart Tolle, pg 186 to 189:
WHO YOU THINK YOU AREYour sense of who you are determines what you perceive as your needs and what matters to you in life - and whatever matters to you will have the power to upset and disturb you. You can use this as a criterion to find out how deeply you know yourself. What matters to you is not necessarily what you say or believe, but what your action and reactions reveal as important and serious to you. So you may want to ask yourself the question: What are the things that upset and disturb me? If small things have the power to disturb you, then who you think you are is exactly that: small. That will be your unconscious belief. What are the small things? Ultimately all things are small because all things are transient.
You might say, "I know I am an immortal spirit," or "I am tired of this mad world, and peace is all I want" - until the phone rings. Bad news: The stock market has collapsed; the deal may fall through; the car has been stolen; your mother-in-law has arrived; (

) the trip is cancelled, the contract has been broken; your partner has left you; they demand more money; they say it's your fault. Suddenly there is a surge of anger, of anxiety. A harshness comes into your voice; "I can't take any more of this." You accuse and blame, attack, defend, or justify yourself, and it's all happening on autopilot. Something is obviously much more important to you now than the inner peace that a moment ago you said was all you wanted, and you're not an immortal spirit anymore either. The deal, the money, the contract, the loss or threat of loss are more important. To whom? To the immortal spirit that you said you are? No, to me. The small me that seeks security or fulfilment in things that are transient or angry because it fails to find it. Well, at least now you know who you really think you are.
If peace is really what you want, then you will choose peace. If peace mattered to you more than anything else and if you truly knew yourself to be spirit rather than a little me, you would remain nonreactive and absolutely alert when confronted with challenging people or situations. You would immediately accept the situation and thus become one with it rather than separate yourself form it. Then out of your alertness would come a response. What you are (consciousness), not who you think you are (a small me), would be responding. It would be powerful and effective and would make no person or situation into an enemy.
The world always makes sure that you cannot fool yourself for long about who you really think you are by showing you what truly matters to you. How you react to people and situations, especially when challenges arise, is the best indicator of how deeply you know yourself.
The more limited, the more narrowly egoic the view of yourself, the more you will see, focus on, and react to the egoic limitations, the unconsciousness in others. Their "faults" or what you perceive as their faults become to you their identity. This means you will see only the ego in them and thus strengthen the ego in yourself. Their "faults" or what you perceive as their faults become to you their identity. This means you will only see the ego in them and thus strengthen the ego in yourself. Instead of looking “through” the ego in others, you are looking “at” the ego. Who is looking at the ego? The ego in you.
Very unconscious people experience their own ego through its reflection in others. When you realize that what you react to in others is also in you (and sometimes only in you), you begin to become aware of your own ego. At that stage, you may also realize that you were doing to others what you thought others were doing to you. You cease seeing yourself as a victim.
You are not the ego, so when you become aware of the ego in you, it does not mean you know who you are – it means you know who you are
not. But it is through knowing who you are not that the greatest obstacle to truly knowing yourself is removed.
Nobody can tell you who you are. It would just be another concept, so it would not change you.
Who you are requires no belief. In fact, every belief is an obstacle. It does not even require your realization, since you are already who you are. But without realization, who you are does not shine forth into this world. It remains in the unmanifested which is, of course, your true home. You are then like an apparently poor person who does not know he has a bank account with $100 million in it and so his wealth remains an unexpressed potential.