How do you know if you've been delusional or just grandiose? Does it have to be bizarre to be delusional? And what is bizarre? Does it have to be rationally impossible to be bizarre, or just extremely unlikely? For example, is thinking you are a different and more intelligent life form than humans delusional or grandiose? Or thinking you are one of the greatest geniuses of all time? (extremely unlikely but not impossible) How about thinking almost everything that happens around you happens to guide your thoughts and actions, i.e. thinking fate only cares about you, where does that belong?