Insightful. To say the least, really insightful. Marking the double minded-ness that we all face and the lack of confidence everyone goes through (maybe you should've named it confidence ).
What i don't seem to be a particular fan of is however the form, though you structured it pretty well, some lines do seem to be kind of extra. A suggestion would be that you look into the Italian (Petrarch-an) sonnets because this could have easily been made into a really good sonnet with the octave surrounding the theme of thoughts which moves into self-doubt in the sestet.
Just a suggestion though, your poem even without structure is well written.