If the way to manifest the life of your dreams is to think all the happy thoughts you would think once those dreams did come true, then it seems to me that anyone can afford to do it.
If the cost of having your dreams come true is to be as happy as you can be right now, before any of it shows up, then that sounds more than reasonable.
After all, if you seriously go about doing this, and all you get out of it is finding a way to be happy no matter what, then it seems to be that you will have won at the game of life.
You want anything that you want because you think it’s going to make you happy. So, why not just get happy now?