Sometimes when responding to a text in quick response, RIGHT AFTER clicking the 'send' button, I'll realize that I have something else to say or maybe forgot to include in previous text. By this time I have to go to home screen or notification panel to start a new message. Since it's so convenient to swipe right or press 'back' to close the window, you should just leave the box open to allow for multiple messages to be sent if necessary; at least as a preference in settings.