We all have an inner dialog going on in our heads at all times. In fact, we often have a lot more than one going on! As automatic as it is, it's important to really listen to it consciously. What we want is to make sure it's positive self talk rather than negative, which seems to be way too common unfortunately.
I have definitely had to tame my inner dialog. For different reasons, I incorporated some very negative thoughts about myself as a child. Circumstances in which I lacked self-confidence would easily trigger these thoughts throughout my life, and I would reflexively think to myself "oh, you'll never be able to do that" or "you're too old to do that" and on and on. (Frankly, it got much worse than those examples.) When I really started paying attention and noticing what I was telling myself, I was shocked. I would never say such condemning things to another person, why to myself? The thing is, I could spend time in therapy and figure out WHY I had all that inner negativity, but I learned that I could heal myself of this self-flagellation without necessarily figuring out the "why." At this point, the negative talk was more of a bad habit than a conviction. Logically, I knew that I didn't really think these terrible things about myself, but it had become a self-destructive and self-sabotaging habit. It was a case of "auto-pilot" steering the plane downward!
Luckily this is something that can simply be reprogrammed. It involves being much more mindful and aware of what thoughts are occupying your mind. You have to take your mind off "auto-pilot" and consciously correct and re-direct any negative self talk that comes into your head. You have to be a sentinel to your own habitual, daily thoughts. There are some specific ways to help yourself do this. I have used self hypnosis very successfully. Subliminal audio for self confidence is another good tool. I felt perhaps the most immediate result when I used a tapping technique to replace my negatives with positives. (Truthfully, tapping is a great tool for many different issues!)
For an even more specifically personal technique, you can write down some of your most frequent negative self talking statements. Then write down the opposite statement, creating a positive affirmation for yourself that directly counteracts your personal issue. Come up with a list of several affirmations to read to yourself daily. Better yet, record audio of yourself saying these positive affirmations and you can play that tape while reading along with it. Doing this every day will help turn your negative dialog into positives and will help you be truly self empowered.