I like coding and designing, but whenever I do either I get too little sleep which makes me lazy.
I find it good to take breaks, not just code, do other things such as play guitar or video games or something that involves *shudders*

going outdoors. Don't forget that coding and designing are just parts of owning a website, and that you should take breaks from doing that to also work on other things like content development, competition research, etc.
Keep goals firm in your mind, and make sure they're goals you really actually WANT to reach.