Seriously, believe anything you believe as long as it isn't of extreme importance to you so as to debilitate you.

In my experience, antipsychotics do a very good job there (together with mood stabilisers for more of the same during mania where antipsychotics may not be enough).

Believe what you believe. If unsure if it is solid: high-pass filter.

Hope this helps but do tell me how you see it differently. I am truly very interested to know.