Dip in Motivation + Lazy = Plateau....HELP!

All, this happens to me a few times a year and I usually just wallow then eventually pull out of them but I thought I would reach out to the MFP community to see how others deal.

Every few months, even if I change up my workouts, diet, routines - you name it - I just can't get fired up for workouts. But the timing on this plateau is horrible for me. This weekend is the start of my (very unofficial) fall race season.

I just hit a wall and completely level off (at BEST) and start to dread my workouts. Totally sucks.

So my question is: How do YOU break out of a rut or bust through a plateau??

Thank you in advance!