There are many ways and reasons to change the normal mental state. It can happen by accident or intentionally. An altered state of consciousness through an illness such as a high fever or deprivation would cause hallucinations and might be a terrible sign. There's schizophrenia, the person has no control over their state and withdraws from reality.
Intentionally includes sleeping, daydreaming, hypnosis, meditation or the use of drugs. Many people sleep and daydream to escape reality, they're happier in their dreams and wish they could sleep all day. Hypnosis can help manage feelings, help someone reach a goal like to quit smoking, and create new behaviors or is done for fun. I've heard that in some cultures meditation is used to reduce stress,
Intentionally includes sleeping, daydreaming, hypnosis, meditation or the use of drugs. Many people sleep and daydream to escape reality, they're happier in their dreams and wish they could sleep all day. Hypnosis can help manage feelings, help someone reach a goal like to quit smoking, and create new behaviors or is done for fun. I've heard that in some cultures meditation is used to reduce stress,