There's plenty things you can do. First off think if you are under stress lately? Is you boss giving you a hard time? Do you have problems in your relationship? If there is no stress in your life than you should start analyzing your every day life routine.
Do you do sports? Are you overweight? Do you have an illness? Do you take any drugs at the moment which may cause sleep problems as a side effect?
You must eliminate your worries in order to sleep better. If you still cannot sleep than you should introduce a prior-to-sleep relaxation ritual. This can include taking a hot bath, reading a book, listening to a favorite CD at low volume and setting the bedroom temperature slightly lower than normal. Because room's temperature is lower your bed feel even warmer and your sleep will be more cozy.
If above sleep tips does not help than perhaps you need to talk to some sleep therapist which will try to help you get better sleep.
Adequate sleep is very important because when you sleep your body regenerates and your mind rests (except for dreaming). Sleep problems may lead to development of sleep disorder (such as insomnia, sleep apnea, restless leg syndrome). If that is the case you should see your doctor and tell him / her about your newly developed condition.