After working in software development for over 10 years I've been part of many late nights, weeks and even months before. Every time I have to work well over the normal 40 hours many things start deteriorating. I am tired all the time, the quality of my work goes significantly down and I certainly have issues concentrating and remembering things. I've had weeks where I've worked 100 hours and I'd be surprised if I was 50% effective as I was working around 40 hours.
When I get into that state, by mind starts to lie to me about the quality of work. I start believing I'm still being effective. Must be some sort of survival mechanism.
Stress sucks and it ruins so much.