Not answering as someone who currently works as a courier but had jobs in the past where I was always on my feet. I definitely get the concern. I’d suggest you keep trying to find something that works for you, but also note that you don’t need to be pushing yourself to your limits every day. As a runner I’ve learned the value of incremental training and pacing yourself. I run every single day, but most days it’s just 1 mile and not nearly as fast as I’m capable of. Even if it was just a half mile or a quarter mile, just ensuring it’s what I can fit in my schedule. Then I use apps like runna to build a plan when I have an actual goal like a serious race. Not saying this is the way, but the principle of finding a lightweight ritual that you do daily might be just what you need if fitting in your own physical activity is important to you, and that’s a good objective to have!