Following [this longstanding request on Meta Stack Exchange](https://meta.stackexchange.com/q/87500/203389) you can now retract flags you have cast.  Simply click the "flag" button again on the post you flagged and the "Flag Answer" (or "Flag Question") button becomes "Retract Flag".  This does not work on comments.  

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/a1YSi.png