I think there are 3 kinds of people.
1) Those who, when they started backpacking, thought. "Wow, this is fun and would be more fun if I went alone." These folks might be like me. We are inclined to want to do things By ourselves. At work if I get assigned to a project to create a new product and it includes "collaboration" and a work group, I ask to be reassigned to a project I can do alone. It's my personality.
2) Those to are okay being alone or with a group. Sometimes they prefer to go it alone and other times with a group.
3) Those who are most comfortable in a group and really don't like to be isolated.
These are personality traits that perhaps we are born with.
Solo backpacking has nothing to do with bravery, courage, self-sufficiency, etc. Some people like it; others don't. Solo is not necessarily good or bad. For me it is my preference 99% of the time.
If you somehow want to go solo, but there is a lurking question whether it is safe, reasonable, etc.; it probably means that you may lack specific knowledge about a facet that has you sitting on the fence. Determine what it is that is stopping you (the "fear") and then research the subject.
Last year I wrote this article on my blog, which included...
"For some reason, I get the greatest criticism about hiking solo from other backpackers. This might infer that backpackers have greater knowledge about the dangers of solo walking than non-backpackers, or perhaps I come across as elitist. I couldn't disagree more. In my opinion, hiking alone is safer than hiking in a group."