We investigate the relationship between self-awareness and dishonesty in a pre-registered experiment with 1,260 subjects. In a first experiment, we vary the level of awareness of subjects' own past dishonesty and explore the impact on behaviour in tasks that include the scope to lie. We find that in single-person non-interactive tasks, self-awareness of dishonesty helps to lower dishonesty in the future encouraging ``moral balancing''. However, in tasks that are competitive in nature becoming more aware of past dishonesty raises the likelihood of dishonesty in the future which we ascribe to cognitive dissonance. In a second experiment we vary the degree of competitiveness in one of our core tasks to further explore the interactions between self-awareness, (dis)honesty and competition. Our results show when and why pointing out those who have been (dis)honest in the past can be an effective way to induce honesty in the future and when it might back-fire badly, and perhaps also shed some light on perceived increases in dishonesty in politics, the media and everyday life.