Best-selling author and spiritual teacher Eckhart Tolle says the key to happiness is to stay rooted in the present moment. Read an excerpt of Eckhart's book, The Power of Now, to find out how to find peace in the present. Then, watch Oprah and Eckhart's complete interview Sunday at 11 a.m. ET/PT on OWN.

See if you can catch yourself complaining, in either speech or thought, about a situation you find yourself in, what other people do or say, your surroundings, your life situation, even the weather. To complain is always nonacceptance of what is. It invariably carries an unconscious negative charge. When you complain, you make yourself into a victim. When you speak out, you are in your power. So change the situation by taking action or by speaking out if necessary or possible; leave the situation or accept it. All else is madness.

Ordinary unconsciousness is always linked in some way with denial of the Now. The Now, of course, also implies the here. Are you resisting your here and now? Some people would always rather be somewhere else. Their "here" is never good enough. Through self-observation, find out if that is the case in your life. Wherever you are, be there totally. If you find your here and now intolerable and it makes you unhappy, you have three options: remove yourself from the situation, change it, or accept it totally. If you want to take responsibility for your life, you must choose one of those three options, and you must choose now. Then accept the consequences. No excuses. No negativity. No psychic pollution. Keep your inner space clear.

If you take any action—leaving or changing your situation—drop the negativity first, if at all possible. Action arising out of insight into what is required is more effective than action arising out of negativity. Any action is often better than no action, especially if you have been stuck in an unhappy situation for a long time. If it is a mistake, at least you learn something, in which case it’s no longer a mistake. If you remain stuck, you learn nothing. Is fear preventing you from taking action? Acknowledge the fear, watch it, take your attention into it, be fully present with it. Doing so cuts the link between the fear and your thinking. Don’t let the fear rise up into your mind. Use the power of the Now. Fear cannot prevail against it.

Read more of The Power of Now