Saying "reality check failed" wouldnt that seem to imply that you were not in reality, "I was checking if I was in reality, and my test failed, therefore, I am not in reality" so arent failed reality check good things for LDS, and successful reality checks bad things for LDs, but good for Real life.

Anyway, I dont even really do RCs in my DILDs, they dont really do anything, you are either dreaming, or you are not, if you cant figure it out just by thinking about it, then your LD prolly isnt going to be clear enough to be really fun anyways.

I determine wether I am dreaming by what my gut tells me. What my gut tells me, and the truthiness of the situation.