The 3DS features a quick save option if you need to stop in the middle of a quest, or you can simply close the lid and put the game in sleep mode until you're ready to continue on your adventure. (gaming-age.com)
You need to leave the path to reach this, so it's best done when you're not in the middle of the quest. (vg247.com)
In the middle of a quest, if you use a hero save and reload the save, you will start at the beginning of the quest as if you had never begun, and you will retain all items that you obtained during the last run of the quest. (gamerankings.com)