I don't take breaks unless I'm on a serious losing streak. That means dropping from 1400+ to 1200+.
It also means your deck isn't good for this week or at the current point of time. Usually, it is the latter. Of course playing skill also matters in getting a good score.
Consecutive losses can contribute to you playing worse, at least in my case. I get to a point where I want to watch my ELO score rise but don't wanna put in the effort to win, which is a horrible frame of mind to be in. If you hit a point where you're losing > 33% of your games it's time to go do something else, or build a new deck. Building a new deck will help you by forcing you to re-examine your strategy more during games.