Don't you hate when you have an idea for a game that you realy REALY want to make, but you can't or you know that, in the end, it won't deleiver the results you want? Or when you have an idea you THOUGHT you realy REALY wanted to make, put in weeks of work and get board of the concept? This has happened to me on 3 occasions already. My most recent flook that I worked all day on, ORIGINS. I knew once I started testing a demo I made that I coundn't make it scary. I feel like ****
I've spent tonnes of time trying to make things that were out of reach, or I became bored of them. It's not really a waste though, because you always learn to do new things or get an idea for a better game idea while you do it (unless you're trying to remake the same game each time ).
Although, if you've only worked on it for a day, you probably won't find it scary. Scary games usually are made with the engine/game control first, and then the scary stuff is put in. Try getting a solid gameplay engine together before putting the scares in.
Also, Sved is correct as well, you know where everything is going to happen (unless you make the scary stuff happen randomly) so you won't be as scared