At the top right of Today’s summary is an editable training-status chip — tap the 
beside it to set where you are right now: Building, Maintaining, Tapering, Resting, Holiday, Sick, Injured, training around an injury — or, for female athletes, Pregnant/maternity.
It’s a hint to the dashboard, not a data override: when you’ve flagged an expected easing (resting, injured, on holiday, pregnant, etc.), a falling fitness trend is read as expected rather than flagged as a concern, and your Today’s Read is worded to match. It doesn’t change any of your actual fitness numbers — just how the dashboard talks to you about a dip that’s happening anyway.
Full explanation: Training Status in the guide.