There is nothing like putting in a good hard swim and realizing you actually went 150yds shorter than planned. That is what happened today but I didn't figure it out until I was sitting on the side of the pool counting my laps. It didn't feel too good to have short changed myself, but I took it for what it was and decided I wouldn't obsess about it too much.
I'll just do what any self-respecting swimmer would do... I'll make it up the next time I am in the pool!