"Listen to your body" is definitely part of it, and I consider it to be the ultimate veto over whatever plans and goals we may have established for training. On a daily basis even. But I don't think it's an answer to training because it's so subjective and dependent on our internal awareness which can be misleading. Plus we all have different tolerances for pain.
I'm going to later put up a summary of the training schedule from the time of injuries until whenever it all stops hurting, under the assumption that what was possible for me - presuming no ill effects - would at least be a baseline that anyone could replicate or push beyond. I've kept a spreadsheet for this year for running and have a log for cycling, so I can know exactly how much I've pulled back or can improve to. Hopefully the detail can be of use to someone - I know that I'd have liked to see something like that.