Insomnia affects many, but if we really want to drop off at night, the key lies in switching off.
Sleep is big news. Just last week, a study into the UK's sleeping habits found that the happier people are, the better they sleep.
Those who are in love with their partner - and their job - have the most restful nights, according to a survey of 14,000 households by the University of Surrey.
But when sleep is constantly elusive, it can be a nightmare, particularly for many, whose lack of sleep is putting them at greater risk of a host of health problems, ranging from depression and anxiety to immune deficiency and heart disease.
In Britain the insomnia problem is so bad that the Mental Health Foundation (MHF) has warned it's a "major public health concern", and has launched a campaign and a report, Sleep Matters, to raise awareness of the importance of sleep.
Dr Andrew McCulloch, chief executive of the MHF, says: "For too long, sleep has been neglected as a major influence on the physical and mental health of the nation. It's crucial we now treat the issue of sleep problems as the major public health concern it is."
Insomnia is a chronic inability to fall asleep or remain asleep for an adequate length of time, usually causing a negative impact on a person's waking life.
In a survey published this year by sleep organisation Sleepio, it was defined as sleep disturbance for at least three nights a week to the extent that it causes a degree of daytime distress.
The survey found that compared to people who sleep well, insomniacs are four times as likely to have relationship problems, three times as likely to experience low mood, lack concentration during the day and struggle to get things done, and more than twice as likely to suffer from energy deficiency.
Sleep expert Professor Colin Espie, director of the Glasgow University Sleep Centre and co-founder of Sleepio, says: "Everyone knows sleep is absolutely crucial, but it's not come into the public awareness in the same way that diet and exercise have.
"Sleep is something that's been negelcted, and if you've got a problem like insomnia, it's really difficult to get any help."
Insomnia has a myriad of causes and a report from the National Sleep Foundation in the US this week has warned that watching television every evening before going to sleep, playing video games late at night, or checking emails and text messages before turning off the lights, could all be interferring with sleep.
The theory is that exposure to artificial light from such gadgets can increase alertness and suppress the release of melatonin, a sleep-promoting hormone.
But hi-tech gadgets are just one type of sleep disruptor. Others include stress, anxiety, depression, ill health, hormone problems, and drug or alcohol abuse.
And while using drugs can actually cause sleeplessness, they can also help you sleep - but only if taken with care.
The study by the University of Surrey found that as many take medication to help them sleep, with women more reliant on it than men - and a need that seems to increase with age.
Chronic insomniac Heath Ledger, star of Batman film The Dark Knight, died of an accidental overdose in 2008, and among the cocktail of drugs he took were various sleeping tablets.
Espie warns: "Many people take sleeping pills for years and years, but they're only designed for short-term use.
"They don't tend to work in the longer term and people can get dependent on them."
One of the major causes of insomnia is stress, and Espie explains that the body goes into arousal mode under stress, and becomes more alert.
"That's a natural response which is there to protect us, but sleep is disrupted by it," he says - and the difficulty is, this response can become a habit long after the stresses have gone.
Chronic insomnia is caused by continuing difficulty in getting your sleep pattern back into shape. People may then become preoccupied and concerned with getting to sleep, and a vicious cycle is created.
"Stress creates vulnerability in our body systems, alertness increases and causes insomnia, which can lead to risks of other disorders, particularly depression," warns Espie.
The MHF says the majority of poor sleepers might benefit from simple methods such as a self-help book or an internet course based around the psychological technique cognitive behavioural therapy (CBT), which encourages a more positive attitude to help break the cycle of negative thoughts which can lead to sleeplessness.
Espie, who has written Overcoming Insomnia and Sleep Problems, a self-help guide to using CBT, says people having trouble sleeping should try CBT to rebuild their sleep pattern.
He advises insomniacs to go back to basics and ask themselves how much sleep they really need, by keeping a diary to record when they sleep well or poorly, and the possible reasons why.
The University of Surrey study, funded by the Economic and Social Research Council as part of its wider Understanding Society study, found one in eight people get less than six hours of sleep a night.
"Work out what your average amount of sleep is, and try to get that amount every night," advises Espie. "Gradually stretch your sleep window and pull your patterns into shape."
He says people often do the wrong thing when they're not sleeping enough and go to bed earlier, so they're not sleeping for an even longer amount of time.
"Narrow your sleep window to make it closer to the amount of sleep you get on average, and once that's consolidated, try to increase it."
Another important way to improve sleep is to develop techniques to slow the racing mind. Espie says CBT is very effective for this, as it takes some of the emotion out of the problem.
"After all," he adds, "Good sleepers don't think very much about the whole thing at all."
The MHF's Sleep Matters report makes various recommendations, including healthcare staff receiving training on how to advise people with sleep problems.
"People are looking for solutions, but those that might work aren't currently being made available," warns Espie.
"If we sleep well it protects us against many things, particularly mental health issues.
"If we can't sleep well, it causes fundamental problems."