You use the ring to teleport back home. You could have just walked, but there are 5 crossings between your house and the park, so you can't be bothered. Nor can you be bothered to wait for the bus, or the subway. Or the other 20 million public transport options Fleuve City has. Once you get back home, both your parents are at work. Your little sister is playing Minecraft in the family room, so she's dead to the world. Perfect. You head up to your room.
You've always been curious about girls, and what it would be like to be one. You wish that you had been born as a girl, and suddenly the world shifts. You get up and examine your room. Everything looks so much bigger! That's when you realize that you are 4 foot nothing. You grab your driver's license, to see that no, you're not younger. You're just short. Wishing yourself back, you decide to transform yourself more... carefully next time around.