Music theory: Descending melodic contour creates a depressed or resigned feel

I read today in "The Complete Idiot's Guide To Music Composition" that descending melodic contour "creates a depressed or resigned feel".

I noticed some examples in songs I listened to today:
The Cardigans - And Then You Kissed Me
Arcade Fire - The Suburbs (Continued)

Tension and Release in action + new album (7th) started

I started on my 7th album the other day called "Audio Artz".

The first track is a good example of "tension and release":

The tension happens every time I loop back to the beginning of the dialogue. Partial release happens every time I allow the dialogue to play out a little bit, but ultimate release comes when the whole dialogue sequence plays out.