I've actually slept though the night for the past two nights for the first time in about seven months! I jokingly told my wife "Something must be wrong. This is not right!"
Shift work will really mess up sleeping patterns. Day shift workers don't normally go to sleep for 6-7 hours after getting off work. Many 2nd shift workers try to sleep soon after getting off, that tends to confuse one's body.
I did many years of shift work and split shifts in my younger days, BD (before diabetes). I did not have many problems until I switched to working 'normal' hours, what a mess!
I was eventually diagnosed with Delayed Sleep Phase Syndrome. Back then the way to cure it was to change your sleep time forward (yes, not backward - trying to go to sleep earlier is a mistake) an hour every other day until you have gone around the clock! It takes aboout six weeks and really, really messes up your life. Going to sleep at 4 AM, then 5 AM, then 6 AM...and so on! But it worked for me.