I take small progressions from different songs. Which songs progressions I will use, depends on the mood.
That right theeerrrr (int), is pretty much it! However, you don't always have to use a different progression, you can stay within the framework of a song/progression and play some minor chords at times within the progression and take the mood from happy to sad.
example...
**movie ex.,***
If you watched "The Color Purple" they played the theme song at different times throughout the movie and used the same song progression, just played differently during the sad parts or the happy parts. The way it was played set the mood.
**sitcom ex.,**
"The Brady Bunch"...they played this song so many ways, I can't even start to explain, but it always fit the mood of the scene even though it was the same progression. "Jamie Foxx" even put a spin on the song musically when he played it...