We don't all fall asleep simply because we're in bed; some of us, at some stages of our lives, will toss and turn and fidget, waiting for tiredness to arrive -

We don't all fall asleep simply because we're in bed; some of us, at some stages of our lives, will toss and turn and fidget, waiting for tiredness to arrive - potentially for hours! - if we go to bed earlier than our body clocks demand.