There is a difference between happiness and wisdom: he that thinks himself the happiest man is really so; but he that thinks himself the wisest is generally the greatest fool.
If the first inward thought is not warded off, it will generate a desire, then the desire will generate a wish, and the wish will generate an intention, and the intention will generate the action, and the action will result in ruin and divine wrath. So evil must be cut off at its root, which is when it is simply a thought that crosses the mind, from which all the other things follow on.