buyers' remorse

Noun

buyer's remorse (uncountable)

1. A feeling of anxiety or regret after making, or after promising to make, a purchase, especially a purchase encouraged by a high-pressure sales pitch.
   • All too often, however, a gal comes home and buyer's remorse sets in. […] A dress looks dreamy when you try it on in the shop. But once you're standing in front of the mirror at home, something dreadful's happened.1953 May 11, “Correct for Figure Faults to Avoid Buyer's Remorse”, in St. Petersburg Times, retrieved 21 Oct 2008, page 26
2. (transferred sense) A feeling of regret after any kind of decision, for example voting for a certain party or consenting to sexual intercourse with someone.

   Synonyms:

   postdecisional regret