Try to go to bed at the same time each night. The body has an internal clock and hormones that control sleepiness and wakefulness.
This clock works best if there is a regular sleep routine.
When working well, you will feel sleepy at bed time. Try not to ignore this by staying up, as this is a window of opportunity for sleep. Going to bed too early can also disturb your sleep. In the hour before going to bed, it is important to have a relaxing sleep routine.