How to Deal With an Anxiety Disorder

I have noticed myself being more hesitant in telling her that I cannot spend time with her because I know that will only leave her feeling hurt. She responded with no but she was still very sad about me canceling and has not been the happiest since two days had passed. There is a lot I want to tell her but feel like I cannot do so without risking me causing a bigger issue. I am slowly becoming mentally burnt out and do not know how much more of this I can take. Thank you for taking the time to read this letter. If it is a little confusing I love you both mentally exhausted bestie.