The goal of this prospective clinical trial is to improve patient compliance and performance of deep inspiration breath hold (DIBH) to further reduce the cardiac dose from left breast radiation, and to improve cooperation and patient satisfaction through an active and formal pre-treatment respiratory training program combined with relaxation training (R\&R) in breast cancer patients undergoing adjuvant radiotherapy for left sided breast cancer. The main questions the study aims to answer are: * Does the use of communication training and the use of relaxation techniques (R\&R) reduce the Maximum dose to the heart (Dmax) and improve further heart dose parameters in deep inspiration during adjuvant radiotherapy for breast cancer? * Does R\&R improve longitudinal anxiety and quality of life under patients undergoing DIBH adjuvant radiotherapy for left sided breast cancer? Participants will be randomly assigned to either an experimental arm, which will receive the R\&R, versus a standard arm that will not receive the R\&R. * training program in the experimental arm includes breath hold training, music, and nature sounds that patients can listen to on an MP3 player * both groups complete standardized questionnaires about their well-being and satisfaction at prospective time points before, during the radiation treatment course, as well as at 6 weeks follow-up Researchers will compare the R\&R group (interventional arm) to current conventional DIBH instruction (standard group) to see if Dmax to the heart decreases and compliance and satisfaction under patients rises.