Yeah I know how you feel! I'm pretty much worthless if I get much less than 7-8 hours of sleep. While I was in the Marine Corps sleep deprivation was just part of the training but I don't believe any Marine to include myself enjoyed it. Sleep deprivation makes even the simplest of task like tens times as difficult it seems. As far as I'm concerned it is a form of torture especially when their is a lot demanded of you at the time. Coffee is great and I love it but its certainly not a replacement for adequate sleep. I've found that coffee can help make perhaps the first two hours or so go by reasonably well but that's about it. How others can actually thrive on 4-5 hours a night and on a regular bases nonetheless is beyond my understanding. I guess some people just require less sleep than others. I think the majority of us however are designed to preform optimal on at least 7-8 hours though so I wouldn't be so hard on yourself as I'm pretty sure you are the norm.