It happens to nearly every single day-hiker: It's a beautiful day, but there is no one to hit the trail with. Hiking doesn't have to be dependent on finding a hiking companion, and as long as common sense is used, hiking alone can be done safely and be an entirely unique experience.
Following these rules doesn't make a solo hike immune to danger -- hiking alone is always going to be riskier than hiking with a friend or in groups.
It's important to be confident about hiking alone -- there's not much point in hiking alone if the very thought makes a hiker nervous. But for those seeking a little mountain therapy and solitude, there's no reason it can't be safely done.