I have no trouble going to sleep but always wake after 4 hours and then, like BlueBelle just "bunny hop (love that phrase!) through the rest of the in- bed phase. Always up before 6am and often by 5am. I seem to function on that so have long decided to just go with it as my pattern.
I read that it was only in the industrialisation of the work force that 8 hours sleep became regarded as "normal" (probably due to exhaustion?). In generations prior to that, it was normal to have two phases of sleep with often activities taking place after one sleep, followed by a second. There are many references to it in literature, journals etc and it seems that was the accepted pattern.