It will be very difficult for you to achieve a full recovery from your OCD if you really do believe that there are things that you should not think.
There are two reasons for this:
1. The idea that you should not think something is just an opinion. Just because you think you should not think something does not mean that anyone else would agree with you. In fact, a therapist will probably want you to think the very things you do not want to think of because this is actually very therapeutic. One of the best tools for fighting OCD is doing the very opposite of what the disorder tells you to do.
2. As we have discussed previously, there is no such thing as a bad thought. A thought is just a thought. We are not judged by our private thoughts; we are judged by our actions and our intent.
So, even if you think that a loved one will be harmed tonight, that thought does not cause the harm to happen. You do not have an intent to harm anyone, and thinking it does not somehow set into motion that process.
Holding the belief that there are thoughts that you just should not have perpetuates your OCD.
It gets you to continue to believe that there is something wrong with the way you think about things, and what therapists try to do in therapy is help people counteract that belief and teach people how to let their thought processes flow naturally.