The instruction we find in books is like fire. We fetch it from our neighbours, kindle it at home, communicate it to others, and it becomes the property of all.
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.
Remember that ofttimes the wisdom of God appears as foolishness to men, but the greatest single lesson we can learn in mortality is that when God speaks and a man obeys, that man will always be right.
The deeper that sorrow carves into your being, the more joy you can contain... When you are joyous look deep into your heart and you will find that it is only that which has given you sorrow that is giving you joy.