Gulf Coast -
Interesting question. I'm sure it varies from patient to patient and probably has a great deal to do with what type of work, age, and abilities after completing treatment.
Personally, my first time through, 1997, I was back to work within six weeks of completing treatments. Within a year of my diagnosis, I was back to my original weight, working out in the gym and my wife was expecting our first child all while working 50 plus hours a week. (Civil Engineer. The physical aspect of my job is minimal.) The second time, 2014, the impact was much greater and I did consider changing jobs to better accommodate my "new" physical constraints. But now, 2 1/2 years out, I'm finally feeling mostly like myself again. If my career was that of a laborer or some other activity that required extended / excessive energy and strength, or was based in clear effective verbal communication, lawyer, I would be out of luck.
I can understand your comment about the emotional struggle. I've been dealing with cancer and cancer related issues for almost 20 years. I like to say that its gets easier, but that's not exactly true. I have learned to enjoy life rather than running through it. Keeping focused on something is the best way to get through the rough parts.
If the changes in your routine due to the new job are causing problems, I would consider looking for something that is better suited for you at this point in your life.
There are no easy answers.
Good Luck