Sentence:  `` Speed in painting a picture is valid only when it imparts spontaneity and crispness , but unless the artist has lots of experience so that he can control rapid <WSD>execution</WSD> , he would do well to take these first sketches and soberly reorder their design to achieve a unified composition . 
Meaning of the word marked with <WSD> tags:  the act of performing; of doing something successfully; using knowledge as distinguished from merely possessing it