How can one tell that they are actually doing something; ie in a Jhanic state or visualizing vibrations vs having a really good imagination?

I'm not trying to troll, I just can't tell. I have a really good imagination. I've been meditating for a while and can "picture" vibrations or imagine blissfullness. Also the idea that Dr. Ingram discusses in MTCB on visualizing the vibrations of momentary sensation seems like it could be imagination as well. How do you tell? I don't want to think I'm actually achieving something when in reality I'm just daydreaming. Maybe there is no difference. And if so, what good does all this do over just concentration mediation?

Thanks