While there are those who are wired to be alone and don't require sharing their experiences, I think most of us do have a basic need to experience something with others. Sharing beauty, awe, humor, or even fear and danger goes back to the beginning of time. Public speaking really has its roots in those cavemen getting together to review the days hunt, who caught the biggest saber-tooth, and who was eaten by one.
When you are out on your own, even if your goal is to meditate and sojourn in solitary with the world, bring a notebook, an audio recorder, or even a FlipCam. Record your thoughts and how you might share them when you return home. You can risk taking mental notes - but depending on how long it takes you to start recording your ideas in your story file or on your blog - that risk can leave an idea floating in the wind.
Talking to yourself has its value. But when you're a speaker - keep your ears open and your keypad open. You never know when the words you say to yourself are the same words your next audience needs to experience as well.