Everything has side affects, sometimes the side affects are much bigger than the main affect.
I guess the question is what affirmation(s) are you refering to?
Here's what I was taught and what seems to work for me: affirmations and sigils need to be phrased in a positive way of speaking. Your subconscious is what's affected by affirmations, and it picks up on connotations easily. So "I am not sick" might seem like a good affirmation, but your subconscious picks up that you are saying "sick" to yourself every day and says, "ok, sick, sick, sick."
So in that case, the affirmation would be better phrased like, "I am healthy" because that word has a positive connotation.
That might be a side effect, if that's the sort of thing you're asking about.
Thanx guys it cleared out my question.
I have heard that affirmations could have side effects. Is this true?