Hi! Have fun, eat well, and get enough sleep! Take care of your health, especially during these last days. Your primary goal should be to finish the game or at least make it playable. All the simple ideas often turn out to be too complex to execute in just one day, haha, so try to listen to your teammates and keep things simple. But a game jam is a great opportunity to experiment and test ideas, so go for it!
Personally, we try to plan to finish the game a day early, so we can use that time for music, fixing technical issues, and designing the game page to entice others to play our game. Have fun, and I wish you an amazing first horror game jam!