Cognitive and affective interrelationships are increasingly gaining importance in educational literature, assigning emotions a prominent role in the teaching and learning process. This study aims to promote awareness among prospective teachers of their emotional vulnerability and the influence of affective and emotional aspects in the teaching of natural sciences, mathematics, and social sciences. The research had a dual purpose: to analyse the beliefs, attitudes, and emotions of prospective teachers regarding the teaching of these disciplines and to examine the impact on their beliefs and emotions after undergoing specific training. The study topic is justified by the growing attention emotions are receiving as decisive factors in learning processes and the persistent substantial gap in scientific education research, particularly in the realm of online teacher training. To address and analyse this gap, a descriptive quantitative survey study on beliefs, attitudes, and emotions towards the teaching of these courses before and after participation in a training program was designed. The analysis of the data revealed results consistent with previous studies. Specifically, the results demonstrated that prospective teachers showed more negative emotions, beliefs, and attitudes towards the teaching of natural sciences and mathematics compared to the teaching of social sciences. However, in all cases, improvements were observed after receiving specific training. These findings highlight the need to incorporate emotional improvement projects into online teacher training, particularly in the fields of natural sciences and mathematics.