Failure is good. Breaking things is good. Don't be afraid of either.
I know a lot of people here (myself including) have really bold ideas of what we want to make. This is a 48 hour jam, don't waste time trying to make the perfect version of your idea. Just build it. Move fast, break things.
It doesn't matter if your game isn't exactly what you imagined, all that matters is you did something.
So get ready, grab some snacks, grab some coffee or tea and build something. Anything. Just build it.