Thanks for the post.
I think the main effect is on the psyche of the person making the affirmation --or Afforemation, which means asking "How can I do/achieve X?" rather than simply stating "I want X."
I definitely agree with your statement that, "if somebody seemingly comes to a decision by themselves, it is much more likely to stick." This is a key aspect of the negotiation strategy that Chris Voss, former lead hostage negotiator for the FBI, describes in his book, "Never Split the Difference: Negotiating as if your life depended on it." I found it both interesting and useful. If anyone's interested, I wrote a mini-review on Steemit.