I can personally identify with this issue, and I know that for those who worry it can be a stressful situation. So, how does one stop worrying about not getting enough sleep? To be honest, I find the concept of worrying a good sign. The reason for such is that it may be deduced that if a person is concern about not sleeping enough is because that person is concerned about their healthy and well-being. If such is the case, this is a good thing. Being concerned about one's health and quality of life is a positive factor and one that should be present at all times. Not only do we become more aware of our bodily functions as well as mental and sentimental stability, but we also focus our efforts on improvement.
Although efforts may be genuine, not a lot of people may be able to efficiently satisfy their drive of health conservation (in this case, sleep the minimum required amount of hours). When this occurs, our health concerns (a positive factor), become a source of worry (a negative factor). Once we begin to worry, not only do we feel bad the entire day, but we also program our bodies to high levels of stress, which in turn affects out bodies and healthy to a greater and deeper level. In other, more simplistic, words, it is a vicious cycle.
So, I would recommend that you try to first evaluate your feelings of worry, and begin to understand that your reasons to feel worry are understandable and even a good quality of self preservation. In doing so, you will be able to manage your stress a lot better. Once you are able to manage ad understand the source of your worry, your worry turns back into a concern that is more manageable, which will allow you to focus on finding solutions.
Secondly, I would try to vent my negative emotions by performing an activity that relaxes me before bed. For me that is drinking chamomile tea and listening to audio books on personal growth after taking a warm bath. In doing so, I am able to distract my mind from the feelings of concern for not been able to sleep enough, which usually inflict with how fast I am able to fall asleep.
Lastly, I have found it helpful to schedule (yes, schedule) my sleeping hours. As busy as this society is, it is important that we not only schedule our working hours, but also our personal hours, which I believe include sleep. Set a time in which you go to bed by, and if your schedule is just too busy, try to arrange your schedule in which a way that you are allowed to sleep an adequate amount of hours at night and are able to take a quick nap.
Remember, a good night sleep will help you have a clearer, stable mind, which will in turn influence your thought process (again, a vicious but oh so lovely cycle).