Mowing the yard the first couple times of the season always involves a (re)learning curve. You have to remember the contours of the yard, figure out where the new low spots and horse-hoofprint-pits are, and take pains to stay out of the pond, avoid low tree limbs, etc. You have to map out your mowing strategy and get your "saddle seat" back.
Then there's these guys. Run through a good patch of these, then get downwind, and whew! The tears may flow!