The CONCEPT of Pink Floyd's "Division Bell" album changed my life; it got me out of eating disorder-habits as one change. It just change my overall view on things..everything.
If you feel like learning more about it:
The Division Bell Concept
Other than that? Pink Floyd means a lot to me...I can easily say that the music has kept me alive. Not exaggerating- think what you want. (And no I don't mean "The Wall" or even "Dark Side of the Moon" but everything, in the literal meaning of the word. I love everything they did.
I like "The Final Cut" less because that's pretty much just a solo album by Roger Waters with a 'guest appearance' by David Gilmour on the song "Not Now John".) Etc.
I won't say that a piece of music in the classical genre has changed my life as I actually do not know a lot. I listen to what I've heard and liked.