Hi [@Brie21]‍ sorry to hear re your diagnosis but good to hear you have a treatment plan in place.

I think the answer to your question is very individual as people have quite different experiences and it depends on whether you have lymph nodes removed and also how long your radiotherapy is for. Speaking for myself I took two weeks off after my lumpectomy but didn't have lymph nodes removed as my wide local excision was treated as another biopsy after two inconclusive biopsies and cancer not formally confirmed until the results from surgery. My rare breast cancer (Tubular Carcinoma) was well contained so lymph node check not needed. I was pretty tired physically for first few days but got out for short walks each day and rested up and felt ready to return to a demanding office job after two weeks. I worked for a few weeks before starting a 5 day course of radiotherapy. I was expecting to feel really tired from that and told my manager I might need a stint of further time off but the fatigue never arrived - I was told that is because I am fit and active so once again that differs by person. I took the week of treatment off to give myself the headspace of going through treatment even though I felt fine really and planned with my manager to take another week or two off with tiredness but I didn't need to and was back working the following week. My manager and my team were very understanding and didn't put pressure on me which helped. I kept up with walks each day and was able to restart running with some gentle runs about three months after surgery. They were really strict with me about not running for two months until healing had taken place but that was fine as I was still getting my head around the whole thing. The emotional impact does take a physical toll as it takes a lot of energy to process what is happening to your life!
 

Hopefully some others will share their experiences too. I know that some  find the radiotherapy really tiring particularly if a longer course than I had.

Take care and I hope it goes well for you xx