While many people can't wait for the end of the working day to get have a sleep, there are people who can't fall asleep. This phenomenon is called sleeplessness. Sometimes a stress simply doesn't allow you falling asleep, but sometimes it becomes a usage for the mind and body. In this case, you should fight that.
In fighting sleeplessness do not apply to medicines. This artificial stuff will only kill you more, it's a temporary effect.
Counting sheep?

Maybe. But, your mind can get you away of that and it may cause you even more tiredness.
My advice is to meditate a little bit. If your body and mind are overall relaxed, the sleep will come itself. Remember, efforts must be avoided, because it's a natural process.