Reference:
I know what you mean - when I was going through all sorts of personal crap it wasn't unusual for me to be up till 4 in the morning and then going to work at 0730.
Mine isn't personal stuff anymore, it's the medical. I'm ok with it now though, as long as I can get done what needs to be done I'm ok. I have never been a morning person, despite years of getting up at stupid o clock to commute across town to get to work or to drive halfway round the country for a 10am meeting. Even when I'd have appointments I'd make them between 11 and 3 so I could wake up late and get home before rush hour, and then do my work late at night. I could never, ever go back to a structured daily 9-5 office based job. I'd need to have some kind of break in the week to get out of the office somehow.