When something is unbelievably beautiful or joyful, you wonder if it is a dream. Often what you perceive as reality is not joyful. When misery is there, you never wonder if it is a dream. You are sure it is real. This is knowing the real as unreal and unreal as real. In fact, all the miseries are unreal. A wise man knows that happiness is real, a quality of your very nature. Unhappiness is unreal, as it is only an affliction of memory. When you can see both as a dream, then you abide in your true self.
A nightmare is mistaken as a reality only while you are dreaming. Keep wondering whether your waking reality is a dream and you’ll wake up to the real.
Illusion is an error of perception and knowing illusion as illusion is knowledge. Our experience of the world is based on perception that is erroneous, so our experience of the world is an illusion. And each experience leaves a hangover that clouds the intellect. The experiencer is the only reality. Look for the seer, the experiencer, in between experiences. Wake up this moment. Shake your head of all past experiences and look at the pure being that I am and that you are.