Sentence:  For, had we no "Mastery" at all over our "Thoughts", but they were all like Tennis Balls, <WSD>Bandied</WSD>, and Struck upon us, as it were by Rackets from without; then could we not steadily and constantly carry on any "Designs" and "Purposes" of Life. 
Meaning of the word marked with <WSD> tags:  To throw or strike reciprocally, like balls in sports.