It's (That's) easier said than done

ImageMeaning:

It's easy to suggest, but hard to do.

You say "It's easier said than done" when someone suggests something, and you think it would actually be hard to do.

Example:

"Forget all your mistakes and start it over!"
"I'll try, but that's easier said than done."

I should just say "No" to him, but it's easier said than done.