The source of Radhika's psychological stress is Internal Pressure.

Explanation:
Internal pressure refers to the expectations and standards that individuals set for themselves. In this case, Radhika wants to do everything perfectly, which indicates that she has high personal standards and expectations. However, this constant striving for perfection can lead to disappointment and stress.

1. Expectation of Perfection:
Radhika's desire to do everything perfectly indicates that she has a strong internal pressure to meet her own high standards. She may have a fear of failure or a need for validation through achieving perfection in her tasks and endeavors.

2. Disappointment:
When Radhika does not meet her own expectations, it leads to feelings of disappointment. This disappointment can be self-imposed and can arise even when others may consider her efforts to be successful. Perfection is often unattainable, and the gap between her expectations and reality may cause frustration and stress.

3. Stress:
The constant pursuit of perfection and the fear of falling short can lead to chronic stress. Radhika may feel overwhelmed by the pressure she places on herself, which can have negative effects on her mental and physical well-being. Stress can manifest in various ways, such as anxiety, irritability, difficulty concentrating, and even physical symptoms like headaches or digestive issues.

4. Impact on Psychological Well-being:
The internal pressure to be perfect can have a detrimental impact on Radhika's psychological well-being. It may lead to low self-esteem, self-criticism, and a constant sense of never being good enough. This can create a cycle of negative thoughts and emotions, further exacerbating her stress levels.

Conclusion:
Radhika's psychological stress stems from her internal pressure to do everything perfectly. This pressure can result in disappointment and chronic stress, affecting her overall well-being. It is important for Radhika to recognize the unrealistic nature of perfection and to practice self-compassion and self-acceptance. Seeking support from others, setting realistic goals, and adopting healthy coping mechanisms can also be helpful in managing this internal pressure.