The increased number of courses taught in an online environment has led to more teachers in need of professional development for online or blended teaching. Although various professional development programs have been scrutinised, only a few studies integrate the feelings of teachers during their professional development process. Teachers' feelings form an inherent part of their teacher-selves and are reflected in their everyday practice. Therefore, this study uses a hermeneutic phenomenological research method to examine the lived experiences -- the feelings -- of educational staff within a professional development program that targets online and blended teaching. The results indicate that teachers experience a large range of feelings and that these fluctuate throughout the program. These include positive feelings of connectivity, responsibility, and satisfaction, but also more negative feelings of chaos and frustration. The recognition and understanding of these feelings can illuminate particular aspects of professional development that are experienced more positively or negatively, which can guide further efforts for qualitative improvement.