It's normal to feel this way from time to time. I don't think
the so called, "nonchalant" people you see around you are that
removed from the thoughts you have. We're only human, and it's
natural to have insecurities.
Afterall, it can't be too rare a feeling if Beck made a song out
of it. 
Sometimes you need to learn how to laugh at yourself, laugh at
life, take things easy, and look at what you've got instead of
feeling shitty over what you don't.