Yes, there are several journals and publications that provide tips for reducing exam stress during the UPSC Mathematics Optional subject exam. Here are some of them:

1. UPSC Mathematics Optional Exam Guide: This guide is specifically designed for UPSC aspirants who have chosen Mathematics as their optional subject. It provides comprehensive coverage of the syllabus along with tips and strategies to manage exam stress. It includes practice questions, previous year papers, and expert advice to help candidates excel in the exam.

2. Mathematics Today: This monthly magazine covers various topics related to mathematics and is a valuable resource for UPSC Mathematics Optional exam preparation. It includes articles on exam preparation techniques, time management, stress management, and effective study strategies. The magazine also provides sample questions and solutions to help candidates understand the exam pattern and improve their problem-solving skills.

3. Journal of Mathematics Education: This academic journal focuses on research and developments in the field of mathematics education. While it may not provide specific tips for reducing exam stress, it publishes articles on various pedagogical approaches, teaching methods, and assessment techniques that can help candidates enhance their understanding of mathematical concepts and reduce anxiety during the exam.

4. Online Blogs and Forums: There are several online platforms where UPSC aspirants share their experiences, study materials, and tips for exam preparation. Websites like Quora, Reddit, and EduRev have dedicated sections for UPSC preparation, where candidates can find advice and guidance from fellow aspirants who have already appeared for the exam. These platforms can be a great source of information and support for managing exam stress.

5. Self-Help Books: There are numerous self-help books available in the market that provide strategies for managing stress and improving exam performance. Books like "The Mindful Way through Stress" by Shamash Alidina and "The Anxiety and Phobia Workbook" by Edmund J. Bourne offer techniques such as mindfulness, relaxation exercises, and cognitive-behavioral therapy to help candidates cope with exam stress effectively.

In conclusion, candidates preparing for the UPSC Mathematics Optional subject exam can refer to various journals, magazines, online platforms, and self-help books to find tips and strategies for reducing exam stress. These resources not only provide subject-specific guidance but also offer valuable insights into managing stress, time, and anxiety during the preparation and examination process.