And, know yourself. I did my first century alone, and did not join groups. Same with my first real climbing century last summer. And, this summer for my hardest ride yet, I will also go alone. I like to do hard efforts alone so that I can really tune into how I feel and not get swept along with anyone else's pace or psychology, and not feel that I need to take care of anyone else, either. Listen to your own intuition about yourself and how you operate best.