I agree with @Afraser about th need to actually practice something positive daily until it becomes a habit. I fell into a bit of a hole after treatment ended but am digging myself out with simplest of things - a daily one hour walk - I am not an exercise person but found this helped a lot with my headspace as well as my health. Some days it’s not easy as I take Letrozole which causes joint pain but find I can walk through it. It also helps me relax and I no longer need to frantically fill in time which was my go to once treatment ended.I also do a gentle stretch and balance twice a week for an hour which also helps. Exercise seems to help with anxiety.