Instead of using a segue to go back to the previous controller you should use the event that was associated with the segue going back to instead dismiss the current view controller (if segue was modal) or pop this from the navigation controller (if the segue was push) and the previous controller will show automatically.
For example, if the modal segue that goes back was being performed when you pressed a button on your login screen, you delete the segue from the storyboard and on the touch up inside event of the button you link with your action that, upon successful login will call:
[self dismissViewControllerAnimated:YES completion:nil];
On the storyboard, you will right click on the button and drag the touch up inside sent event to the first responder of the view controller scene. This will execute the reverse transition that was executed when you performed the segue transition. You can use a modal segue for that, no need to use a navigation controller.
If you pushed the login view onto the navigation controller, then you have to pop it from the stack (if going back to the previous view). Use one of these:
[[self navigationController] popViewControllerAnimated:YES]; // goes back to previous view
[[self navigationController] popToViewController: myViewControllerAfterLogin animated:YES]; // goes back to specific view on stack.
[[self navigationController] popToRootViewControllerAnimated:YES]; // goes back to first view on the stack
The animated transition should reverse the type of transition used on the segue, so curl up will be curled down when you dismiss the view.
