How to avoid cutting corners when turning right when driving??

I’m a learner so I’m still taking lessons. But a problem I keep having is cutting the corner. My instructor tells me not to slow down until the last minute but I find slowing down before the turn is a lot easier🙄 I suffer with anxiety too so I panic very quickly. If I feel I don’t have enough time to change to gear and turn smoothly and accurately I drive on and my instructor gets mad. I don’t do it on purpose I just freak out. Any tips that can help me out before I go in an hour? I get so scared.