Mostly we don’t go back in life - to anything, really. We’re not designed that way. But unless we have big changes in our lives, the ‘normal’ can seem pretty unchanging. Then we get cancer. It’s not just the effects of the treatments but also the unnerving realisation, possibly very new and most unwelcome, that we are not immortal. What we mostly want is to go back to that happy state where that realisation didn't impinge. Any changes to our emotions or energy caused by treatment just exacerbates the perceived difference.
Counselling may help - your emotions are affected by cancer not just your body. Hair and nails unfortunately take their own sweet time and hair may change quite a lot before it settles. See this as a time for trying new looks - if you can’t beat’em, join ‘em! Exercise is good, if you use a gym I’d be surprised if there isn’t at least one other person there on the same journey. Talk to your GP and counsellor about tiredness - busy, social, working women may see expending huge amounts of energy, without actively seeking to renew that energy, as normal. I certainly did. Changing my attitude (no, not stopping just rethinking) changed my wellbeing.
There will be a new normal if you let it develop - and it may be better than the old normal. Best wishes.