The courage to be yourself is one thing; the courage to GO OUT ON YOUR OWN is entirely another. Most people do not have this strength. Keep in mind it is a practiced confidence, not a quest for invincibility.
The foundation of my choices goes way beyond the labels of being single or married, man or woman, young or old. I hope you will value the art of solo travel after pondering these misconceptions, disclaimers, and results.
THE MISCONCEPTIONS
1) Women traveling alone are in constant danger.
If this were true, I'd already be dead.
Learn: to not be in the wrong place at the wrong time.
2) Solo travel is boring.
It's only boring if you are a boring person. Sorry.
Learn: to read, write, dream, watch, listen, talk, or sleep, in that order.
3) You'll get lost and never find your way back.
If anyone would do this, it would be me, and clearly, I keep finding the way back.
Learn: to memorize and understand maps, and ask that random person on the street where the heck you are.
THE DISCLAIMERS
1) I'm a married woman and I go on trips by myself.
My he-might-be-a-feminist-husband doesn't "let" or "not let" me do things, and I don't "let" or "not let" him go to Harry Potter movies. We just do the things we like to do because we are still ourselves, and this is what attracted us to each other in the first place. Remember, it was his idea to keep my maiden name. "Swags is who you are," he told me, "and I want to be married to Swags, not Vilas."
2) If you disagree, that's fine, but don't try to "bring me back from the dark side;" I've already seen the light.
I know it's not traditional for a woman, let alone a married woman, to travel alone. Guess what: I wasn't traditional before I got married, and the most traditional thing about our marriage is that we trust each other as best friends and partners. Come to think of it, that could be considered nontraditional these days as well. So never mind, we are totally nontraditional, and I travel solo all over the place.
3) I've traveled with and without all kinds of people to all kinds of places with all kinds of transportation.
I continue to find that my favorite adventures have been: solo. I go solo for the same reason you like traveling with certain people more than others. It's not that I don't like you, I just happen to really enjoy being by myself!
THE RESULTS
1) I see.
I actually do not observe things when I am with other people. I am so intent on listening and talking and paying attention to whomever I'm with that I just don't look around me. So while I'm having great investment and return in a conversation, I'm missing everything I came to see and think about. (This is one of the reasons I've been able to enjoy having friends visit Paris; I've already had my moments with the places and am now ready to share them as the background to a dialogue.) When I'm alone, my senses are open to observing beauty, strangeness, history, rhythm, and reality. I need these observations to understand my surroundings.
2) I decide.
I am most decisive in two settings: when I'm in charge or when I'm alone. I can plan, I can change, I can add, and I can subtract all throughout the day and entire trip, with no one to blame but myself. I can decide to sleep all day on the beach, or march all day up and down hills. I can eat snacks all day, or just two huge meals and be totally fine. My decisions don't ruin anyone's life, and the solo adventure skips along a pure and unaffected path. Everyone's happy.
3) I learn.
Even though I'm mostly alone, I still do enjoy talking to people. I always meet the most interesting people (usually other solo travelers, of course) when my attention is not preoccupied by travel partners. "Alone" equals "open" in the world of travel. In 3 short days in Barcelona, I learned: it snows in New Zealand, Irish accents are a lot easier to understand than Scottish ones, Marseille feels safe to a Canadian who works in Tanzania, Southern Hemisphere English speakers can tell the difference between their accents (South Africa, New Zealand, Australia, etc.), Australians don't say "shrimp on the barbie," India is an exceptional place to visit if you accept it for what it is (instead of hoping it will be like America, for instance), and people in Barcelona speak Catalan (not Catalonian!). Art, architecture, culture, food, streets, language...it's all there if you are free to focus your attention on it.
I really encourage you to be open to trying out solo adventuring. It may not be as extreme as hitchhiking to another country, but it can be just as rewarding to go to the local museum, take a road trip to a national park, or going anywhere alone that most people consider it "normal" to go with another person (movie theater, dinner, wedding, etc.). Just have the courage to go out on your own!
If you're hungry for more inspiration, the following reads definitely helped bring me to this point. Stand alone, they are great books, but for the aspiring adventurer, they are gold.
Royal Road to Romance (Richard Halliburton bums his way through Europe & Asia in the early 1900s.)
The Walking Drum (Fictional Kerbouchard sojourns throughout the European and Muslim world of the 12th century.)
Fahrenheit 451 (Fictional future where books and ideas are illegal, and why free thinking is fundamental to a progressive society.)
The rest of the Barcelona series:
Barcelona: The Basics
Barcelona: Gimme Some Gaudí & Jazz
Barcelona: Plaças i Passeigs