In The Lifelong Activist I talk at length about how destructive negative thinking is - and, in particular, the particular form of it that exaggerates one's perceived failures and flaws while minimizing or even ignoring one's successes and strengths.
Just this weekend, as it happens, a woman with whom I was speaking on a business matter told me she was "really could use help" with her time management, citing as proof the fact that we were working over the weekend. She had forgotten, however, that the reason we were doing so wasn't because of anything she had done, but because I hadn't had a chance to return her call during the week. So here she was, blaming and condemning herself for something that wasn't even her fault!
Along with pointing that out, I also pointed out that she did great at her complex and challenging job, a sign that, contrary to her words, she probably was a competent time manager. "This isn't even my main job!" she exclaimed. Turns out that she held a part-time job in addition to a rigorous full-time one AND was a single mother.
I was astounded, and pointed out to her what would probably have been fairly obvious had she not been too negative: that, being competent in not just one but THREE enormous areas of responsibility was a strong indicator that she was actually a great time manager. Of course, she probably wasn't getting done everything she wanted to get done - few of us do - and maybe her system could use a few tweaks here or there (I don't know her well enough to say), but overall she seemed a paragon of productivity.
After telling her this, I could hear the relief in her voice at the thought that maybe she wasn't the bad time manager she thought she was. A burden of self-doubt and shame had been at least partially lifted.
Being too negative in your assessments of yourself undermines you, so work to replace negative beliefs and perceptions with more objective ones. I.e., not, "I never get enough done therefore I must be a terrible time manager," with, "Even though I don't get everything done I wanted to get done, I still got a lot done, so I must be a decent time manager." If you've got a habit of negativity, the first few times you do this you may feel like you're being "Pollyannish" or too soft on yourself. You won't be, however - in fact, such a feeling is a sign you're doing it right. Eventually, you'll naturally adopt a more objective, positive self-image.
Then, go out and help everyone else you encounter be less negative about themselves as well.