twice now I have been up so late that I just pray Fajr before going to sleep.

you remember when you pulled your first all nighter and it felt so unnatural you thought maybe the Universe in its order and logic might not permit you to start a fresh day without having slept first?

Yeah, it felt unnatural sort of in that way. Like "well... it is sort of like I've prayed six required prayers today..." which somehow just feels wrong.

but on the other hand, I've concluded that there's nothing "natural" about getting up to pray at 6am to pray neways, and while I do love seeing sunrise after prayer... (ahem) on the few occasions that i have managed to get up for fajr (oh please, like you do it every day)... generally at that hour i prefer closed eyelids and a sleeping brain. Still it is a nice thing to do.