No one should be afraid to be alone. It isn't as scary as everyone believes it to be. Living alone allows you to find yourself. And as cliche as that sounds, being able to be secure in yourself is important if you ever want to cohabit with anyone.
For many people, they've never lived alone. They've always been with their family, or college roommates. Breaking out on your own, and stepping away from the craziness that is having other people in your house is a great way to rely on yourself and only yourself.
Relying on yourself is important because you can gauge where you're at in life. You can learn what you are good at and what you need to improve on. Maybe you need to perfect your cooking, or your cleaning skills are lacking. When you're by yourself, you can't blame anyone else for your house looking like a mess, or not having food prepared, because it's all on you. You can only hold yourself accountable.
While you are by yourself, you do the typical soul searching that is associated with living alone. You figure out what you want in life. You have more time to do things for yourself and by yourself. You learn how you want to live. When you learn all these things, it keeps you from settling when you move back in with someone.
Also, when you live alone, you aren't truly alone. You can get a dog, or a cat, or a goldfish. Having the company, someone to depend on you, without trying to control the household, that can be good for some people. You can still go out with friends, visit family, and travel. You aren't constricted to the confines of your house by any means.
Living alone should be an exciting time in your life, not a scary one. So if that opportunity presents itself, take it. Take the leap of faith necessary to live by yourself and be truly independent. It will be worth it.