I wish I had a good suggestion for the anxiety many survivors feel when having a mammo. Truthfully--and I don't want to sound insensitive in any way--I'm very fortunate in that I don't have this kind of anxiety over any medical testing. But I do have genuine anxiety over other issues (e.g., the thought of getting Alzheimer's sends me into a panic, especially as I saw my mom suffer with it for 10 years and her sister and her mother and her mother's sister). So I can relate from that perspective, and I'll tell you how I handle that in case it's useful.
1.) I tell myself that no amount of worrying about it will make it not happen if it's in the cards, so I may as well enjoy life.
2.) I tell myself that I have done everything I can do to prevent this from happening so if I do get it, then I'll deal with it.
3.)I distract myself by thinking about almost anything else. (That works well for me as I'm easily distracted.)
4.) The moment I begin worrying, I immediately think of someone else who's going through a difficult time and then actively do something for that person. This can be a simple as sending a card. (That works the best for me.)
5.) I remind myself that all I am promised is today, and if I start worrying about tomorrow today, then I won't even have today.
I don't know if any of that helps, but even if it helps one person, it was worth writing.
Hugs & prayers,