There's no short cut to learning a new language, you just have to keep plugging away every day.
この場合、次のように言えます。
ーThere's no short cut to learning a new language, you just have to keep plugging away every day.
「新しい言語を学ぶのに近道はない。毎日コツコツやるだけだ」
to plug away の代わりに to hammer away 「コツコツ取り組む」を使って次のように表現することもできますよ。
ーYou just have to keep hammering away every day.
「毎日コツコツ取り組むだけだ」
ご参考まで!