Ehm... Idk. Maybe look for tips to be prepared for what's coming and how to prevent it. Take a deep breath say f- it and just press the button without thinking much. You might regret it after clicking it, but you'll already be in the game, so...

You will have to face your fear and get used to jumpscare, remember that in FNAF 4, you are never 100% safe and you should always expect the worst, this will not take away your fear or apprehension, but it will prepare you mentally, thus reducing the scare.