Most make sure you can actually believe it before affirming it. If it is too strong, water it down a bit and start with that until you grow more in faith. Come up with a variation that you can believe and that suits you. It does no good to repeat something you cannot believe. Even if you are tying to build faith, do not stretch too much. Start with something you can comprehend and after that your faith will build and you go to the next level.
To say something you do not believe over and over, can actually work against you. If your conscious mind rejects it, that rejection will get passed on to the subconscious. Do not allow that. Only speak that which will build you up.
