DIBH anxiety post treatment

I couldn't hold my breath, I waivered too much and couldn't stay within the "lines" I was meant to.  When I went for the practise of the DIBH I went well the first time, then the following two times I couldn't do it, and they knew I would have trouble as I had double appointments (both breasts), so they found another way around it, I am not sure exactly how they did that!  The radiation therapist said they have other ways for people that cannot manage to do the DIBH correctly, I just kept breathing too deeply, I could hold my breath, but not at the consistent depth.  I have had follow up ECG's and heart scans etc. and nothing sinister going on, and I hope it stays that way :)