maybe it's just good pissed-off weather? I've been kinda over-stressed with *everything* lately myself. And ... I've probably overthought some of my problems and underthought others.

Were you already in a mood before mowing? Could it be the mowing is part of it? (allergens - pollens and mold spores, etc; and pollution if it's a gas mower - could affect your mood...)

Of course... this all just adds onto the fighting illness thing. When I'm physically down, it doesn't take much to put me in a bad emotional / mental mood too.