The belief that anything can be undone. Doing, without considering the consequences.
The world we live in suffers from Undoism. People are unwilling to accept responsibility and are always hoping for a chance to do it again or fix it. People wish and sometimes assume that they can CTRL + Z their way out of things. That's probably why so many people are in prison and why so many marriages fail.
Many times, you don't get a second chance. Just ask a member of your local bomb squad.