The reason why reassurance is so bad
Reassurance feels incredible. It makes you feel like you have been saved from this hell.
BUT…. Once you have received information or a perspective that reassures you, your mind will analyse it and fixate on it until it finds faults and flaws. The reassurance will then stop protecting you from your OCD, it will stop feeling meaningful or true. Your OCD will come back and it will feel devastating to have a relapse
Learning to sit with uncertainty by doing ERP shows your brain that uncertainty is not going to kill you. This is why ERP works so well