It is a mistake for a sculptor or a painter to speak or write very often about his job. It releases tension needed for his work.

Moore is warning against over-verbalizing the creative process. For a sculptor or painter, the work depends on a kind of concentrated, pre-verbal energy—intuition, uncertainty, and sustained desire to solve visual problems in material. Talking or writing “very often” about one’s work can dissipate that pressure by giving premature closure: the artist feels they have explained or justified the work instead of making it. The remark also reflects a modernist suspicion of programmatic statements and manifestos, implying that the artwork should carry its own meaning and that too much commentary can harden into formula, narrowing experimentation.