OCD and anxiety are actually really easy to understand.
Imagine that for some reason someone becomes afraid that their house will fall down if they don’t hold it up, so they start holding up the wall.*
They know the house probably won’t fall down if they let go of the wall. They also really want to let go because holding up the wall all the time is exhausting and limits their other activities.
But what if the house really did fall down, all because they made the decision to stop holding up the wall? They wouldn’t be able to take back the damage caused by that one bad decision.
So they keep holding up the wall.
The problem is that as long as they keep holding up the wall, they will never have the opportunity to find out that it won’t fall even without their efforts.
This is how OCD and anxiety work. You’re afraid that if you’re not careful enough, something really bad might happen. You don’t necessarily think it will, but you’re afraid to take the risk; that one bad decision could cause damage, and you won’t be able to take it back if it does. So you play it safe, through avoidance and compulsion.
Because you play it safe, though, you never give yourself the opportunity to find out that nothing bad would happen, even if you were less careful.
The only way out is to take your hands off the metaphorical wall, and see what happens. This is the purpose of Exposure. By doing the things you have been afraid to do, you give yourself the opportunity to have learning experiences that contradict your fear.
*Thank you to Dr. Elna Yadin for this excellent metaphor