Recently a powerful technology has emerged that helps you uncover previously unnoticed evidence about your behaviors. This science is part of the emerging field of positive psychology, as espoused by Martin Seligman, PhD, in Authentic Happiness. His approach teaches specific skills for collecting this evidence from your life; you can then use it to refute any negative messages that you tend to dwell on. You expand your awareness of yourself by looking laterally" - in directions different from those in which you are accustomed to looking - to find other truths about yourself that you have been overlooking or discounting.
It's as if you've taken off blinders - you can see "the other side"; that is, the truth of counterbalancing arguments based in reality. Over time, use of this approach will reveal a bigger truth that you have likely been ignoring by habitually focusing on one tiny aspect of your reality that has become deeply ingrained.
Seligman describes other techniques for expanding your self-awareness. One is the process of savoring positive experiences that counter your familiar negative ones. You can consciously set up time to have pleasant experiences. Focusing on the pleasure available to you expands your repertoire. You can share these experiences with someone close to you, savoring them together in real time; you can reminisce about experiences from the past (recycling them); you can take mental snapshots while a savored experience is happening, to make it more indelible in your memory; or simply immerse yourself more deeply by describing it to yourself as you experience it.
Building a stronger self-concept might well begin with learning to accept compliments. These gifts, like gems, are being handed to all of us all the time. Even if the people in your immediate environment don't seem to be giving them, nature itself is showering them continually - a fresh breeze, a purple and orange sunset, a spring rain. Simply opening your eyes and cultivating gratitude as a way of being can show you many good things to talk to yourself about. You can make Thanksgiving Day happen every day of the year.