I'm not clear on the difference between Quedar and Quedarse when expressing results. The lesson says to use quedar to emphasize a result, and to use quedarse to express the result of a change. What's the difference, please? For instance, the following two examples seem pretty similar to me:
Seguro que quedarás contenta con tu pelado nuevo.
I am sure you will be/end up pleased with your new hair cut.
¡Laura va a quedarse pasmada con la noticia!
Laura will be astonished with the news!