Jon Levy has recently stopped in to get a couple workouts in on his own. They happened to be 2 really tough WOD's. The "Filthy Fifty" and "Eva" will both test your will. Besides his great performances on both, I was most impressed by his willingness to do these alone.
I have a tough time doing "Metcon" workouts on my own. I will simply push harder with company. I like the support of someone cheering me on and I like knowing someone is fighting the same battle with me. The tougher the workout, the more I embrace company.
As a whole, CrossFit is a group fitness program. Most of us find comfort in going through tough physical challenges with other people. We are sharing a common goal. We are feeding of each other's energy and drive. We know if we fall, there is someone there to pick us up. Still others may find training solo suites them better. Is this a personality difference that shows in choosing individual vs. team sports? Does the competitive nature of CrossFit motivate you? Do you feel "pressure" in keeping up when others are around you?