I can, but I rather have it dark.

It's very understandable that it is hard to sleep with the lights on. Your body produces this hormone melatonin, that assists in managing your sleep/waking cycle. When it is dark, your body produces more of it, making you sleepy.
So if you have the lights on, chance is that your body doesn't start increasing the melatonin production, thus keeping you awake or at least have you wake up during your sleep.