Sometimes, when I'm daydreaming, I get really into it to the point that I almost start physically "seeing" the daydream. This happens particularly with sexually arousing daydreams. For example, I'll start fantasizing about a love interest and I'll literally start visualizing it so much that I start to tune out all sights, sounds, etc. around me. All I start to see is the daydream, and it seems real to me.