ADR, you have written posts like this quite a few times. I have written similar ones in the past and I don't judge you for writing them because i know that the mind is totally malleable, this isn't the "real you" and neither is any set of personality characteristics or actions or whatever. So you can forget about being sorry or worrying that you are stuck the way you are or anything like that.
What you do have to realize is that every time you follow (believe in) your thoughts and moods to the extent of writing posts like these you are setting yourself up for similar failure in the future. When thoughts and emotions like these come up, notice them, experience them, but don't get into a struggle with them. Don't "invite them to tea" as they say in Zen.
In my experience if you no longer invite a certain belief or emotion to tea (instead just noticing it when it comes up, and letting it take its natural course) then it will simply become more and more peripheral to the point where it is not emphasized at all by your attention. It will just be like any other sensation in the body, just a happening in awareness without any meaning or importance given to it. Without the emphasis and the visceral holding of the sensation of the thought it simply won't bother you anymore.
Obviously you are dealing with thoughts along the lines of "my practice isn't working, everyone else knows something I don't, i have to figure out (through analysis) how to practice correctly". When such thoughts arise, simply stop giving them importance as described above, be impeccable in your heedfulness remembering the suffering they have caused you in the past.
http://www.ajahnchah.org/book/Opening_Dhamma_Eye1.phpThe Buddha, having contemplated his mind, gave up the two extremes of practice - indulgence in pleasure and indulgence in pain - and in his first discourse expounded the Middle Way between these two. But we hear his teaching and it grates against our desires. We're infatuated with pleasure and comfort, infatuated with happiness, thinking we are good, we are fine - this is indulgence in pleasure. It's not the right path. Dissatisfaction, displeasure, dislike and anger - this is indulgence in pain. These are the extreme ways which one on the path of practice should avoid.
These 'ways' are simply the happiness and unhappiness which arise. The 'one on the path' is this very mind, the 'one who knows'. If a good mood arises we cling to it as good, this is indulgence in pleasure. If an unpleasant mood arises we cling to it through dislike - this is indulgence in pain. These are the wrong paths, they aren't the ways of a meditator. They're the ways of the worldly, those who look for fun and happiness and shun unpleasantness and suffering.
The wise know the wrong paths but they relinquish them, they give them up. They are unmoved by pleasure and pain, happiness and suffering. These things arise but those who know don't cling to them, they let them go according to their nature. This is right view. When one knows this fully there is liberation. Happiness and unhappiness have no meaning for an Enlightened One.