I've always phrased it tongue-in-cheek:
"The first 90% of the work takes 90% of the time. The last 10% of the work takes the other 90% of the time.
"The first 90% of the work takes 90% of the time. The last 10% of the work takes the other 90% of the time.
http://en.wikipedia.org/wiki/Pareto_principle
I've found it to apply to many things in life.
Edit: why would this be downvoted?
There have been several times where I've accidentally upvoted low-quality (sometimes malicious) posts, and I never feel good about it.