You can't just decide a vote doesn't count because you don't like the outcome, though. Setting that precedent would mean no one who disagreed with a result would ever accept its legitimacy. There has to be a limit set somewhere.
A vote passing is not a suicide pact that locks you into that course of action between now and the heat death of the universe. It's possible to pass something, and then do another vote, later, to revert the changes you've made.
Likewise, in a parliament, you can keep bringing an issue up to a vote over, and over, and over again (See: Everything that Congress did after passing Obamacare). There's occasionally some set of procedures that prevents this kind of denial-of-service from being used all the time... And occasionally not.
This happens in referendums, as well. The same issue appears on the ballot every few years, until the people pushing it get 50% + 1 support for it.
It's often the only way to actually get social progress. Keep hammering on your pet issue, until enough people agree with you, and it wins.
As long as you're not breaking any laws, or referendum procedures, it's completely fair game.
It's occasionally used when voters realize that what they voted for was incredibly stupid. So yes, you do get take-backsies in democracies.