Summary: Users often make mistakes or change their minds. Allow them to exit a flow or undo their last action and go back to the system’s previous state.
Users will feel a sense of freedom and control using your product, if they are able to abandon a task easily, return to the previous step, or undo a change they’ve made to the system’s state. Think about creating clear exit points and 'undo' features, so that users could feel control over the experience, rather than be at the mercy of your design.
Link to "User Control and Freedom"
Link to info poster with tips & tricks