Thank you for this! As coach for high performance atheletes this seems as very mild Statement.
...The answer to this as far as I am concerned is boringly simple. Listen exclusively to your feelings. Ignore most other metrics (time, efficiency indicators, etc). For me (as well as for many many among my followers), resuming after a long time off is = to meeting with a very good friend I have not seen in a long time. It's a special moment, not a painful one.
What makes it so special is that it seems like we "rediscover" swimming. Not quite where we had left with all our ??? and issues, but from the perspective of feeling. ...
Never read a boring answer from you! You're absoultly right. Think have to be more aware of Kaizen's point of view in future. Even if the improvement has to start several steps again which were stil taken in past times...