Something that is "easier said than done" - in other words, this idiom used as an adjective - means, something that is more difficult to actually do in reality, than to promise, pledge, or vow to do it.
This is a very common phrase in North America expressing that boasting of doing something before you have actually done it is easy, and worthless. Something easier said than done is something harder to do than it is to boast of doing it.
So, do it.
Example: Billy and Carol are at a karaoke. Billy: "I'm going to sing this song a lot better than Ray over there." Carol: "Easier said than done. He's pretty good at this. Are you?"