我不坚强但我不为你懦弱
[wŏ bù jiān qiáng dàn wŏ bù wéi nĭ nuò ruò]
I'm Not Strong, But I Won't Be Weak For You. It means while this person knows they're not the tough type, when facing you (or possibly a situation concerning the addressee), they still try to show strength instead of giving off a weak appearance.