In Tristram Shandy, fate rules your… fate. Everything happens by design, and no individual is master of his own destiny. At the same time, maybe Tristram has it wrong. He also claims that the reason for his bad luck comes from his father's interrupted ejaculation, which is his mother's fault, or, if you want to really trace it back, maybe put it all on Mr. Shandy. In any case, it's certainly not Tristram's fault. There's no such thing as free will in Tristram Shandy. If you think about it, a novel in which no one can make choices is duller than dishwater. If everything is pre-determined, then there's no suspense. In fact, moving away from "fate" as an answer for why things happen is a hallmark of novels, so it's telling that Tristram Shandy insists on fate. Sterne, are you messing with our heads again?
Tristram does not really believe in fate. The way he discusses his accidents—for example, by calling his circumcision "Susannah's accident"—suggests that he blames individuals for what goes wrong.
Tristram Shandy suggests that the only choice an individual can make is how to approach life.