A change is as good as a rest continuing one's efforts but changing the form of activity is as refreshing as a respite; proverbial saying recorded from the late 19th century.
change one's tune express a very different opinion or behave in a very different way.
change the name and not the letter, change for the worse and not the better reflecting a traditional belief that it is unlucky to marry someone whose surname begins with the same letter as one's own. Saying recorded from the mid 19th century.
don't change horses in mid-stream do not try to alter a course of action once you have embarked on it; saying recorded from the mid 19th century. The phrase to change horses in mid-stream is often found.
See also change-ringing, ring the changes.