Okay, magic trick for all you Duo users who wanna keep your streak alive but have horrible memory:
If you miss a day, go into your settings and manually set your phone date to the day before, and then do a lesson on Duolingo. If you're learning Korean, Japanese, Russian, whatever that has another alphabet, you have to do an actual lesson and not practice otherwise it glitches and won't work.
Once you do a lesson, reset it to the real time and then do another lesson just to lock in. Your streak will be saved and Duo will have no idea. I've done this 3 times. My 393 day streak is so safe yippe