I've noticed that when i'm "balls deep" in a pyschedelic adventure, smoking cannabis at that point more often than not causes me to get dizzy, confused and a little frightened. Last time i ingested a couple grams of cubensis and started freaking out uncontrollably after smoking a bowl of mid-grade cannabis. i eventually vomited and my ego began to feel "safe" again. That was not the first or only time thats happened to me, so i imagine it can be common for others. i recommend sticking with the meditation and concentration on comfortable ideas/activities. Combining psychedelics can be dangerous.