The most important aspect of travelling alone is to understand how dependent our lives have become on things which hardly mattered a decade ago. Independence of mind and independence of thought is difficult to attain when bombarded with the irrelevant information of daily lives. It is when we are travelling alone and have only ourselves to rely on, that we come to value independence.
Further, travelling alone means there are no limits on you. You can be your true self, get wet in the rain, eat at a shady restaurant, drink with unknown people and come out richer with the experience of it all. There are very few ways in which we learn as much we do while travelling, and travelling alone is even better as we become our own teacher and guide.