dream

Conventional: An imaginary experience the mind has when it loses consciousness of “reality” (as in sleep), or when it hopes for something better than “reality” (as in “hopes and dreams”).

ACIM: All experiences the mind has within the world of time and space, including the world itself, which are simply imaginary experiences your mind has while asleep (see sleep) in Heaven and unaware of true reality. Just like nighttime dreams, this world seems to be reality, seems to exist outside your mind and independent of it, seems filled with things and people that are not part of you, and seems to cause you to feel things. Yet, also like dreams, it is an escape from reality, a fantasy, which exists within your mind and was caused by you. Just as nighttime dreams are your protest against the insults of daytime “reality” (see CE T-18.II), so daytime dreaming is your protest against true reality.

Conventional experience and states of mind in this world are described as nightmares. These are painful because you seem to be attacked from outside and because you do bad things that seem to warrant punishment. Release comes from realizing that they are only dreams, that you are the dreamer who made them up.
You can choose that your nightmares be changed into happy dreams, forgiving dreams. From these you can awaken to reality. See CE T-27.VIII-XI.