I've also been thinking about working hard at work to further your career. Normally, I don't do this; but there are occasional periods in which I do.
Right now, I'm thinking I should never do this. Assuming a normal software development job market, I should probably only work hard on things that I think are intrinsically worthwhile, which is my natural mode of operation. Then, I should (honestly) just try to sell what I do instead of trying to bend the natural trajectory of my work.