There are a few great laws that govern all thinking, just as there are a few fundamental laws in chemistry. We know that thought control is the key of destiny, and in order to learn thought control we have to know and understand these laws.
One of the great mental laws is the Law of substitution. This means that the only way to get rid of a certain thought is to substitute another one for it. You cannot dismiss a thought directly. You can do so only by substituting another one for it. If I say to you, “Do not think of the Statue of Liberty,” of course, you immediately think of it. If you say, “I am not going to think of the Statue of Liberty,” that is thinking about it. But if you become interested in something else, you forget all about the Statue of Liberty; and this is a case of substitution.
When negative thoughts come to you, do not fight them, but think of something positive. Preferably think of God; but if that is difficult at the moment, turn your attention to something quite different.
But I say unto you, That ye resist no evil! (Matthew 5:39).
With him is wisdom and strength, he hath counsel and understanding (Job 12:13).
When dealing with things we have been unable to eliminate as sources of stress,anxiety or fear, we must substitute thoughts of the positive alternative to that which plagues us. The most universal positive thoughts are about God. More specific thoughts can visualize a successful outcome to that which is causing our negative state of mind. Counting our blessings is a sure way to substitute for generalized negative states. Another sure bet is to recall beautiful experiences of the past or anticipated joyful events in our future. Whatever techniques fits the situation, the action is still the same. We must direct and control our thoughts to a better place. With time, this becomes less challenging and with practice will become our natural way of thinking. That is when we can live immersed in the joy, faith and hope of the garden each moment of each day we have left.
Substituting,
Z gardener
Good Morning Garden 
Giving thanks in all things (1Thessalonians 5:18) seems like strange advice until you recognize the power of it to transform your mindset. As simple as substitution is as a concept, the doing of it takes some real perseverance. To the victor goes the crown!