If nothing (and no-one) else, your protagonist should end the story in a different state of mind to the one they began in, unless you're deliberately putting them back exactly where they started to show their lack of change or to emphasise small changes...
Going from a negative to a positive emotion gives the ending a greater positive impact because the reader is subconsiously aware they've been on an positive emotional journey with the protagonist.
Given examples:
Biggles and Tintin frequently follow this arc:
Boredom -> Increasing Determination -> Satisfaction
Some of the Nancy Drew books often do something similar:
Curiosity -> Increasing Fear -> Relief
The Harry Potter books are much more complex, containing multiple arcs, one of which is:
Alone -> Increasing Friendships -> Loved
H.R. Filmore's Reminders to Self, December 2012
