Congratulations! That's a huge jump in mileage, almost 30%!! And in hills!! There is just nothing as cool as going the longest distance ever- running or biking! (I wouldn't know about swimming :-)
100k is an important milestone, too. For me, after that, longer distances just seemed a little bit easier than the distances leading up to 100k. It's like your body gives up and says, ok, she's going to ride a _long_ time, I'd better cooperate now since I can't talk her out of it...
Yeah, I know those last five miles, too. They can be difficult no matter _what_ distance you are going! I always tell myself- it's only five miles. That't like riding halfway to the store (or whatever). Works for me!
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"...I'm like the cycling version of the guy in Flowers for Algernon." Mike Magnuson