Sleep when you are sleepy. :)

Insomnia it's not a physical problem. Probably you're worried about something inside your subconscious. ps: i don't sleep since 1995 )

You should have an healthy life to have a good sleep.
However when it happens, the worst thing to do, in my opinion, is to stay in the bed. The mind will be full of thoughts, anxiety and other stupid stuff.
Could be better going in another room and read a book, or make some deep breathing and after a while, when the sleep is coming, you could come back into the bed.
Other thing you can do are meditation, some tecniques of relax..
The yoga is very useful for that... ;-) ...I know
Ciao.

It is a real problem and one that needs to be really discussed and not replied to in short messages. Much depends on the individual case. If you would like to meassge me and explain your situation then we can explore the reasons and the remedies toether, 

try not to sleep in bed, tell yourself you must be awake all night, although it seems counterintuitive at first it will take your mind from sleeping which is what keeps you awake in the first place.