I did not find it particularly hard with therapists and don't tend to have much conscious fear of rejection in general. When it is hard though (not only in therapy but everyday relationships) is when I am avoiding admitting something about my contribution to the relationship, avoiding responsibility for something I do or how I handle something. It is hard typically when I am already aware and sense that something is off - in other words, I am in a state of cognitive dissonance but not yet ready to resolve it. I can also describe it as momentary avoidance of responsibility for my own role and actions. This is an area where I feel I have improved tremendously in the past ~10 years but still happens at times. When I am not so aware, then usually I behave in a more dismissive way, which is basically ignoring things and trying to move on without tapping into it and resolving it - and my own reaction is the rejection. We can of course describe this as a form of fear of rejection - I reject you first, so you won't even have a chance. I imagine that for someone who has a more preoccupied style about relationships and attachment, it manifests more as intense fear of rejection/abandonment, which is discussed on this forum a lot? In any case, I believe that the culprit is always some form of fear and anxiety.