I often find that when I am anxious, meditation becomes much harder! I find it harder to breathe and become increasingly anxious until I feel so disrestful that I give up. Any ideas for how to overcome this?

The thing that helped me most was bringing awareness to my body. I start by slowing down to the best of my capacity and narrow in my awareness to my big toe, then the second, the third, the fourth , the fifth, the sole, the heel, The ankle, the shin etc etc to the rest of my body. Applying this method with any intense emotion works wonders.