Insomnia is the inability to sleep at night.
We are all unable to sleep at will.
The conscious mind cannot choose to sleep at will.
It can choose to stay awake, for a limited period, using will power.
Sleep is when the unconscious mind is awake.
Insomnia is the state of being awake too long.
It is the state of sleeping less than is believed to be essential.
Defining enough wake time & enough sleep time is a conscious decision that will influence our sub-conscious action.
Insomnia is the belief that there is not enough sleep time or too much awake time.
Choosing enough is not usually a conscious decision.
Allowing the unconscious mind to regulate sleep requirement will result in having enough as a balance between conscious & unconscious wake time.