I have read couple of books about working process, time management and how to do your work better, the most common thing mentioned there is the importance of taking a break.
Taking a break is crucial, because then you concentrate on your free time, doing stuff that you love and most important - have fun. You go out with friends, play video games, read books, have some time for thinking. Having fun and forgetting about your work is the best way of getting fresh ideas and inspiration, if not for this at least you will get a good rest.
People lie to themselves that, when they work more, their chances to success are bigger. Success happens when you work smart, not when you work your ass off. People who say that they can’t afford a break, because they have to invest 100% of their time in their projects are not working smart at all, because taking a break is part of the work. This should be taken seriously, think of your free time as part of the working process, it could cost you loosing the next big idea.
Don’t ignore your free time, just enjoy it and even if you don’t come up with a new great idea, you won’t regret being well rested and happy.