Hello @scram,
It is indeed a balancing act. I'm fairly new here and have a similar diagnosis and story to yours. Left breast, early breast cancer grade 3, hormone positive and I had been just over 5 years clear from any testing of a previous cancer. I'm just over 2 weeks post surgery, very much in the discomfort zone. So I get your shock, disappointment and frustration.
The group is very welcoming and helpful. I'm at the one day at a time, do what I can do for the day and if I make it out of bed great, if I don't there is always tomorrow. As @arpie has mentioned, there are many resources. For me, I've started to see a specialist physiotherapist who will help with movement and avoiding Lymphedema and nerve cording. I also recommend the BCNA gentle pilates videos https://www.bcna.org.au/resource-hub/articles/strengthen-your-recovery-pilates-program/. All the best with your healing.