I agree with everything that has been said so far.
And I'd like to add one thing I noticed when I started experimenting with affirmations. From my experience , before trying to change other beliefs, first you should realize whether or not you believe you can change. It seems funny because if you compare what kind of person you're now and the way you were 10 years ago, you can see that you have changed, whether because you wanted it or some external factor forced you to. I've often heard people say 'there's nothing you can do about it, things are the way they are, it's just the way it is' etc.
So first I decided to get clear whether or not I believed I could change in certain area. Then it was all about finding the right strategy or technique to do it. Affirmations were just one of those things and they didn't seem like lying but only a step in the process of change. For some issues they worked and for others they didn't (or not yet anyway).
Just my 2 cents