For me at least I can train myself to go to bed at 10PM with discipline, but if I miss one day I find myself back into the natural groove of going to bed at 2AM. I do not expend effort to sleep at 2AM, I expend effort to sleep at 10PM. When I am jet lagged my body is confused and does not quite know when 2AM is, but eventually it figures it out and we're back to square one (Google "zeitgeber" for how it figures this out, but subjectively I assure you my body does the adjusting, not me).