It is true that the better you get at any skill, the more aware you become of potential areas for improvement. However, this does not mean that the better you get at X, the worse you feel you are. In fact, the opposite is likely true: as you become better at X, you are likely to feel more confident and competent in your abilities.
The process of improving any skill involves learning from mistakes and setbacks. As you learn from these mistakes and setbacks, you become more aware of your weaknesses and areas for improvement, but you also become better equipped to tackle them. As you become capable of addressing and overcoming these weaknesses, you gain confidence in your abilities, and your overall feeling of competence and self-esteem is likely to improve.
Moreover, improving in any area also brings with it a feeling of accomplishment. As you get better at X, you are likely to take pride in your progress and feel more satisfied with your performance. This can be a great source of motivation, as it provides an incentive to keep striving to improve and reach the next level.
It is important to recognize that improving at X can provide both a feeling of accomplishment and a heightened awareness of areas where you can still improve. It is wrong to suggest that the better you get at X, the worse you may feel you are.