Lily, of course every (maybe not every) hard work leads us to success, bu it's already the upshot of hard work. It's the result of having such hard work that demands more time, energy and makes you feel tired. Without this kind of "unpleasant" process you cannot succeed. That's why we should keep in mind that hard work is only the way directed to success, but not the success itself. Before success you have a lot of challenging ways to go through, which is called hard work. May be that's why it seems unpleasant.