If you have a Losing streak it can be many different things.
Maybe the Losing streak came out of nowhere and you just gotta play the next day for it to be better.
Maybe you gotta addapt to your new Elo with your playstyle. (maybe playing more passive is gonna do the trick or more aggressive)
Or maybe you just gotta let it go and wait for the next day, since Losing streaks happen aswell.
Or maybe you're just bad idk xd
Or maybe you're playing too many champions that you haven't played before/are not your strong champions, you might end up **experimenting too much** when you have a Losing streak. Sometimes it's best to accept "well there's that losing streak" and just wait for the next day.
**I know that sounds boring, but the best thing you can do at all times is just wait for the next day and play like you've played when you were having Winstreaks. And addapt to the situation. Do small tweaks, don't reinvent the wheel.**