The amount of sleep necessary will vary with individuals and with the strain on the individual body. Nervous and tense people usually require more than those who are of a placid disposition. The average individual maintains his health by about eight hours of sleep.
Older people require more sleep than young people, as a general rule.
The inability to sleep your usual amount is called insomnia and this is a problem for millions of people. Exercise during the day will often help a person to sleep better. Try to establish a regular bedtime and go to bed only when you are tired. If you just cannot sleep get up and read. The inability to be able to sleep can happen to anyone.