Wearing the mask alone for some time during the day may help you get used to how it feels and make it easier to fall asleep at night.
Machines with the ramp feature that slowly and gradually increase the air pressure to your prescribed pressure setting as you fall asleep may make you more comfortable at bedtime.
Following good general sleep habits also are helpful. Exercise regularly and avoid caffeine and alcohol before bedtime. Try to relax. For example, take a warm bath before you go to bed. Don't go to bed until you're tired.