How to make sure our thoughts do not put us in denial

If, for example, someone creates the thought of being in a happy marriage, and really believes it, how to make sure he is not in denial and in fact not willing to see a toxic relationship, let’s say, with who resembles a narcissistic pervert?

We know the mind can sometimes put up false beliefs to cope with a painful reality (for example in the Stockholm syndrome). So how do we make sure the thought is going to support the overall development of a healthy personality structure and not encourage a person into being under control?