Contrary to popular belief, working the hardest and the longest hours is not the path to management. Sure, in some companies maybe, but if that's the way to get to management in a company, I'd swiftly exit said company. In that type of environment, the "higher up" you get, the more doggish hours you're working.
Let's face it... who is happy with their first choice of careers? Few people start with something and stick it out forever. Even successful athletes start other careers and you should too. The challenge is to use your first career to build up skills that are needed in all industries, all organizations and all situations.
Have a routine that you use to start your day that becomes automatic and thoughtless. It's really hard to write a 80,000-word novel, but it's very simple to write down 500 words every morning if it's so embedded into your routine that you don't even have to think about it (and at that rate your novel will be complete in just over five months).