Hi there -
I'm 58 years old and a year out from a unilateral mastectomy and radiation (now on an aromatase inhibitor (Anastrozole) and protein inhibitor (Verzenio). I, too, was very out of shape. I feel fortunate that our local hospital has a Lifestyle Medicine dept with a small gym. I used their "Lifestyle 365" program to jumpstart getting back into shape and lifting weights carefully (I have osteoporosis). This type of gym in the hospital is super comfortable because it's just patients trying to get better and hospital staff. Now I'm out lifting on my own and have more confidence.

What has really helped me is to have what I call a "fitness challenge" in the future - something to look forward to and "train" for. For example, last year I made it a goal to briskly walk a half marathon in the Seattle Marathon (here's a little video that I'm in about training for the 1/2 marathon after cancer: https://vimeo.com/1031362655/a4134f6708). Now I'm focused on the "Base to Space" event which is walking up stairs on the outside of the Space Needle (40 stories). It's not so much that I really care about a half marathon or walking up that many stairs, but getting in shape for these small "fitness challenges" motivates me to stay off the couch and it's fun to get out in the community where you're all trying to meet those goals.