What I'm trying to say: "If I don't take a break from studying now, I'll probably forget everything I've learned."
What I'm saying: 「私は今勉強するのを休まなければ、私が学んだすべてのものを忘れるだろう。」
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Sign up to join this communityBy break from study I assume you mean an arbitrary 15min/30min break, not to stop studying for a greater amount of time (like quitting university because of the stress of study). It is also assumed you are not wanting to say this in any type of Keigo nor any type of colloquial dialect.
In that case 休憩{きゅうけい} would be a better alternative that 休{やす}む which in this case may imply the longer break.
今{いま}すぐ勉強{べんきょう}から休憩{きゅうけい}をしなかったら、すべて学{まな}んだことを忘{わす}れてしまいます。