Isaiah 58 and Not Speaking Your Own Words: Question 38

Courtesy of JD Hancock

There's some real puzzlers in this passage:

Isaiah 58

13 If thou turn away thy foot from the sabbath, from doing thy pleasure on my holy day; and call the sabbath a delight, the holy of the Lord, honourable; and shalt honour him, not doing thine own ways, nor finding thine own pleasure, nor speaking thine own words:

14 Then shalt thou delight thyself in the Lord; and I will cause thee to ride upon the high places of the earth, and feed thee with the heritage of Jacob thy father: for the mouth of the Lord hath spoken it.

Question:

What does it mean "not doing thine own ways", "nor finding thine own pleasure", "nor speaking thine own words"?  How do we tell the difference between delighting in Shabbat and delighting in our own pleasures?  And what possible pragmatic application might we find in the enigmatic instruction to not speak with our own words?