I was lightheaded and walked around in a fog during a few days when I started. I got over it, so I assume it just goes with the territory for some people.

You know yourself best. For myself, I found that being really strict actually kept me from quitting because I lost the hunger and the cravings that way. It's not fun for the first week or so, though. After that, I got a lot of energy, felt terrific, and was so relieved that I just didn't even want the carbs any more.