Hi everyone, in a few months (hopefully) I will get a master degree in physics and I have been wondering a lot about making of fundamental research my career (if I manage to, that is). Sometimes I have moments of strong self-doubt since it seems to me that my knowledge is never deep enough and I feel like there's almost a fog I can't see through around certain concepts. Now over the years I've learned to love the whole process of working hard to get around this wall and to overcome the frustration it carries along, but still I wonder whether this difficulty is the sign of a below-average mind trying to grasp ideas beyond its reach or that's just part of the experience of many professional physicists. So what's it like for a successful physicist? Do you experience these moments too and reproach yourself about not remembering the logic behind something you had already understood?