Its a mind thing. Let me give you some insights.
When you close your eyes, you are starting to talk to yourself trough thoughts. ''Ohh god not again, i cant fall asleep, i just want to sleap, i cant do it''
Notice your inner voice is fast and panic, the clock is ticking, you dont look at the clock anymore, the clock is looking at you''
Next time, slow your inner voice down, slow it the heck down. ''iiiiiiiiii caaaaaaaaaaaaannnnnttttt tttt gggggeett nnnooo sleeppppp''
You will get sleepy trust me.