The way I understand it is through the concept of "focus". I have had numerous lessons with spirit in which I have come away with the mantra "Focus on 100% positive".

As I said before, adversity exists and always will exist, however(!) it can be out-of-sight-out-of-mind depending upon our focus. Let me relate this story/example:

You are walking along the beach barefoot having a lovely time. The sun is shining warmly and your feet are cool against the wet sand. Your friend is walking along with you but she is stepping gingerly. She is afraid of stepping on a sharp shell or piece of glass because once when she was young, this is what happened to her. She cut her foot deeply. She is not nearly as happy as you are, yet you both walk along the same stretch of beautiful beach. In fact, if her fear of the potential of getting hurt is too great, walking on the beach might actually be a torturous experience for her.

And yet, the beach is the same physical place for you as for her. So why are the experiences so disparate?

The sharp shells on the beach are there whether we encounter them or not. That is adversity. It is potential that exists at every moment and will always be there. But if we can remove our focus from that potential, then a vast majority of the time we are happily enjoying the beautiful aspects of the beach. It definitely is a challenge to remove focus from the sharp shells when you have been cut by them before, but this is the way to mastery and it is well worth the effort - to learn to see the good amidst the possible bad. Because despite desires, thoughts, etc., "bad" will continue to exist and will pop up when the situation calls for it (or when divine will dictates, or however you wish to view it as fate, purpose, karma, soul plan, etc.). But living in anticipation of those moments makes for a life of misery.