Meaning of 言うは易く行うは難し in Japanese

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Definition of 言うは易く行うは難し

いうはやすくおこなうはかたし(iuhayasukuokonauhakatashi) 【言うは易く行うは難し】

They say you shouldn't take rumors seriously, but that's easier said than done.

彼かれ、能書きのうがきばかり立派りっぱだけど、言うは易く行うおこなうは難しかたし、ってこと分かってんのかなあ。

His boosterism makes it sound wonderful but I wonder if he understands how hard it's going to be to actually carry out.