Sometimes you do face such a problem esp if you had any stressful event even otherwise sleepcycle gets disturbed. Try and avoid sleeping in afternoon, keep fixed time for sleep esp waking time fixed. Avoid caffeine after 6pm, avoid TV,  computer, phone 1hr before sleep time, drink warm milk and have have warm water bath half hour before you go to sleep. Exercise 45min everyday. Don't keep checking time if you not getting sleep just relax and listen to some soothing music or read a book. This might help you