I think fatigue varies greatly. My husband has a very hard time with fatigue and is on Orgovyx & Abireterone.
Some days we can get in a great workout, others he’s completely exhausted. Some days a long walk - others days a short one. And yes, some days he just can’t and he needs a full rest day. He used to exercise hard every day before our cancer journey started so it’s difficult for him.
If you have had depression fatigue previously I’d discuss it with your doctor. Battling cancer takes a lot out of you, physically and emotionally.
Wishing you all the best