Get back on the horse/in the saddle

To get back on the horse, or get back in the saddle are idioms that mean to renew any endeavour after a setback. Its origin is obviously equestrian but its coinage and first usage are uncertain. It appears that the 'saddle' version precedes the 'horse' version because Google N-Grams date the former from the 1920s, and the latter from much later in the 20th century. Remember, however, that Google N-grams search thousands of books for instances of the word-strings, which may include literal uses as well as idiomatic uses. Idiomatic usage appears to have really taken off in the 21st century.