I am afraid of you, lest I have bestowed upon you labour in vain.
I am alarmed [about you], lest I have labored among and over you to no purpose and in vain.
I am afraid of you, lest by any means I have bestowed labor upon you in vain.
I’m afraid for you! Perhaps my hard work for you has been for nothing.
I am afraid for you, lest perhaps I may have labored in vain among you.
I am afraid of you, lest perhaps I have laboured in vain among you.
