"There are days when I'm so excited about the future and enthusiastic about what I would like to accomplish in my life," one of my children said to me recently. "But there are mornings when I all I want to do is stay in bed. Why do I feel so differently on different days? Does it have to do with the weather? Or how I slept the night before? Why can’t I always be happy?"

My first reaction was to say, "Welcome to the real world, kid..." But, seriously, hers was an important question. While we all have our ups and downs, there is always a cause for the "downs," and our first step in dealing with these downswings in mood is to identify their source. When we complain to our doctor of an ailment, the doctor’s first concern is to identify the illness. Only once the source of the illness is identified can the curing process begin. "Knowing the sickness," say our sages, "is half the cure."

If you wake up one morning and feel down, the first thing you should do is to try to identify the thoughts that are going through your mind that put you in this state. These can generally be divided into three sources:

1) They may have to do with something external. Perhaps someone has done or said something to you that has made you upset, our something has happened that is upsetting to you.

2) Alternatively, it may be something internal, such as a physical illness which is affecting your emotions.

3) The most common source, however, is your own imagination. You may imagine that someone is planning something against you or something bad is going to happen to you in the future.

In most cases, it is the third category that is the source of our depression. It is our imagination that goes wild and causes us to worry and be fearful. I like to say that the word FEAR stands for False Evidence Appearing Real. Being that the evidence is only in our imagination, we need to take charge of our thoughts, instead of letting our thoughts take charge of us.

In the hard drive of our brain we should have a folder in which are stored backup files of positive thoughts and reminders of all the good things that we are blessed with. We should refer to these files on a regular basis, so that our brain creates shortcuts to them and quickly open them when necessary. Moreover, when negative imaginings bring on negative thoughts, we should use our positive files to do a quick "replace."

Things to put in our positive files folder include thoughts such as how fortunate we are that we woke up this morning, unlike others who did not; that we can see, breathe, walk, etc. But most of all, the thought that G‑d has taken the trouble to create me, a unique human being with a unique DNA, unique mind, unique personality, unique talents — a unique human being who has never existed before and will never exist again. G‑d puts His trust in this unique me and wants me to always remember that I am special, and that the purpose of my existence is to achieve the mission I was created for, which is to make this world into a better place.

My child told me that she knows all of this and has heard it before, but still has trouble controlling her negative thoughts. She knows what to do, she said, but does not always do what she knows.

I reassured her as follows: "The more you practice the 'search and replace' technique and the more you tell yourself that you are really in charge of your thoughts, the easier it will be for you to actually accomplished this. Although we cannot completely eliminate all negative thoughts and down days, which are part of human nature, we can train our minds to replace our negative thoughts with positive ones, and it will take only a split second to jump from being very down to being extremely happy."

Try it — it works!

The ideas in this article are based on a letter from the Lubavitcher Rebbe (Igrot Kodesh, Volume 14, page 22).