Well, I have yet to meet someone, who didn't go through that phase after receiving their black belt. As a matte through that, I went through that phase after each grading, the only difference being, it took longer to get over it each time.
With each grade, you kind of open a new door, with many new and strange things behind. Keep training, enjoy it, and be prepared, when you get to 2nd dan, it probably will be just the same (or so I guess, not having been there yet).
It is the same after your nidan exam; did my test a couple of weeks ago. Yup, similar feelings as after shodan, just a little different somehow. Maybe I will be able to put my finger on it.....by sandan.
Apparently, also the same after rokudan if my sensei is not pulling my leg.