Really there are two beliefs that are the foundation of the statement “I can have, be or do anything I want”, and those are: 1) that you understand that each and very possibility at every moment of time is available in the “field of all possibilities”. 2) That the Universe wants us to have everything we desire and wants us to live easy and happy lives.
So in order to say the affirmation and in order for it to work for you, you first need to bring yourself to a place of believing the two foundation beliefs.
If you understand how the emotional scale works and how it brings to us, from the field of all possibilities the things that we are vibrationally lined up for, then you are half way there. And if you understand the fact that that which we call God or the Universe is a loving entity, that always sees us from a place of love, then you are all the way there. If you need help understanding these concepts check out the video recordings of webinars I have offered in the past below.
Unlimited - 40 Day Law of Attraction Workbook to Accelerate Manifestation