good riddance

Although I have heard the phrase "good riddance" used negatively - "He lost his reelection bid and good riddance to him" - the phrase really means to happily get rid of something that is considered worthless. I suppose in that example the speaker does consider it happy and the loser as worthless. 

It is often used as an exclamation to indicate that a departure or loss is welcome. For example, "We got rid of lots of old clothing we never wear and good riddance to it." 

It is often used as a standalone exclamation - "Good riddance!" but the original full saying is "good riddance to bad rubbish."

We don’t use the word "riddance" anymore, apart from in the phrase "good riddance." Riddance is an obsolete word, but in Early Modern English it was a regular and useful word.

The phrase originated in William Shakespeare's 1609 play Troilus and Cressida. The word "riddance" itself has been recorded since 1525–35, and means the act of clearing away or out, as anything undesirable, or relief or deliverance from something.

Rid + ance is Middle English but Middle English it comes from Old Norse rythja which meant "to clear" and described clearing land of trees and undergrowth. This gave rise to ‘free from rubbish or encumbrances’, later becoming generalized as "good riddance to bad rubbish." 

The Arrow of Deliverance, print, after Arthur Murch, Dalziel Brothers