Lyric discussion by TheBigKahuna 

Cover art for I Gotta Feeling lyrics by Black Eyed Peas, The

Judging from my analysis of these lyrics I believe the author is conveying some inner urge that is both dark and sinnister. This conclusion was brought on by the two segments of the song being very much at opposite poles. As to what this act would consist of, I am unsure, but my leading theory is that the author is a form of Sexual Sadist, hiding behind what the public expect of him. Even in the positive section of the song we see traces of the negative section:

"I can feel.. Tonights the night "

The are even hints of agression in this "song" (or confession as it should be refered to as):

"Just take it off"

"Go out and smash it"

This agression can be attributed the authors intentions or past acts of sexual sadism. Even the way in which the chorus is repeated over and over shows the author is living this past act over, and over. This is most likely an attempt to sooth the inner demon which craves the pain of the innocent. But this repetitive endulgance can only do so much in the long term, and from what we see in the lyrics its usefulness has reached its end and as a result: "Tonight's the night"...