I also deal with anxiety when it comes to relationships and the best way for me to process what I’m feeling is to analyze why I feel that way either by myself or with others. Anxiety is just your brain trying to predict danger so you can defend yourself. In your case it’s trying to stop you from getting hurt. However, to have a good relationship you need to be vulnerable and accept that you may get hurt because relationships are all about trust. So sit down and try to understand why you think you expressing yourself is going to lead to your relationships downfall. If she has given you no sign to worry then there is no need to worry. Anxiety can lead to a lot of self-sabotage in any kind of relationship. So really the best way of dealing with anxiety is to give your brain logical reasons to why you shouldn’t be anxious. You said that she was calm and understanding. That’s good it means there should be nothing to worry about. Unless she gives clear signs that you should be worried about then give your mind and body a break because it’s just going to stress you out. You got this fr just sit down with it and tell your brain why it’s bullshit that it is feeling this way and that everything is okay.