The way what you think will give you certain emotions, and fear is an emotion and happiness is an emotion.  So in a way what you think can control how you will feel.

How our thoughts affect our mood?

A lot of people for instance are often disappointed and they often have such high expectations of them selves that they often feel like they can never reach what they need to reach. They are always running behind things and they always feel almost depressed because of that.  And of course it becomes very hard if that's the way you have to live your life.  If you want everything to be perfect, it's easy to be disappointed.  And  when you are disappointed you start saying it to your self:  "Ah why can't I ever do this or that?" or "Why is it always like that with me?" "Why  do I have to feel this?" 

If you are mad at your self, you are giving your self the worst emotions and your body is going to respond by giving you a certain symptoms , by making you depressed, by making you frustrated.
There is a great book called "Emotional Intelligence" written by Daniel Coleman. It's a bit difficult book, but it's important to know how to control your emotions. That's what he saying in his entire book.

Emotional Intelligence(EQ) is much more important than IQ these days because if you can control your emotions, you can decide when you want to be happy or when you don't want to be happy. And quite often the entire situation, the level of stress that you will feel, will change simply because you give a little story to something what's happening. 

There are a lot of things that are happening outside of you every second. And you always tell little stories inside your head to decide what's that means for you. That's the little interpretation that you give in your head. I'm going to tell you a little story right now, that's going to show you the difference.

The story about one married couple Bob and Branda.

Suppose we have a man and his name is Bob. Bob has a wife and her name is Branda. They have a marriage but it isn't the best marriage any more. They don't really fight but the love isn't the way it is supposed to be. Bob promise Branda that he is going to mow a lawn this Saturday. Branda has to work on Saturday so she is out of the house. Bob wakes up in the morning, his wife is already gone, he  gets out of bad and  opens the curtains. He sees that it's raining.  And this is what happening.  Bob has to give an interpretation,  Bob has to tell him self a little story right now to see what this means to him.

Pessimistic approach.

At first Bob might say: "Oh it's raining :( And I was supposed to mow a lawn. What am I going to do right now? :( I don't know how to solve this problem. I don't know what I can do right now to make this go away. And my wife is going to be mad at me. What am I supposed to do? I can do other stuff in the house but she wanted me to mow a lawn. My entire weekend just wasted. On Monday I have this important meeting and I don't want to have a wasted weekend."  And he continues to talk like that and guess what his  day is going to be like. He is going to be frustrated and depressed because of stuff that's happening outside of him that he can't control ( that's life!) but he wants to control it. So he is mad and guess what  his mood is going to be like, when his wife come home. It might be possible that there will be fight against them, simply because Bob has been messing up his own mind the entire day. 

Optimistic approach.

Now there is another way that Bob can talk to him self when he sees that. He opens up the curtains yet again and it's still raining. And Bob says: "It's raining. I don't like when it rains because than I can't mow a lawn and I promised my wife that I was going to mow a lawn. Why did I promise that to her? Because I wanted to do something for her. I wanted to show here that I love her. What else can I do? I know that she likes lasagna and thinks that I can't cook, but I actually do know how to make lasagna. We've been married for 35 years and I have never made her lasagna, so I'm going to shop today. I'm going to buy all of the ingredients and by the time she comes home tonight I will have made here the best lasagna ever. She is going to be happy. And the entire day Bob looks up ingredients, he looks up recipes and things that he can do for his lasagna. He goes to shop, he goes to the grosser, he creates the lasagna. His wife comes home the table is all set, the wine is there.

What is his life going to be if that's the way Bob thinks. If that's the way Bob tells him self stories when stuff is happening outside of him. His entire life is going to be different. And everything is going to be different. But everything outside of him is still the same. It was still the saturday, it was still raining. His marriage was still not the best. But the way he talks to himself is changing everything that he is feeling. He had a great Saturday, he had any anxiety or frustration and any depressive feelings simply because it was HIS decision.

It's always your own choice.

He can decide to say "Oh it's raining :(" or "OK it's raining. What else can I do?" It's his focus. It's him. It's always your choice. If you have a panic attacks , it's not your car's fault, it's not the fault of the restaurant , of the tunnel, of the bridge, of the meeting,of the plane of the whatever you are afraid of. It is your choice to have a panic attack. And this is something that you probably don't want to hear because all of a sudden, you are responsible for this. That can be the bad news. But yet again... There is another way that you can interpret that. If you are responsible for this, than you can take it away.The things that you need to do are already inside of you.

Few words about self-confidence.

Another example:  if the way you talk to yourself is bad you might have low level of self-confidence for instance. Imagine that you are walking in the street and all of a sudden there is a group of kids that just passing you by. And they start to laugh just when they passed you. What are you going to say to your self? Some people would say : "Oh - oh what's wrong with my hair? " or "Why are they laughing at me? What's wrong with me?" They think it's their fault, they don't have a lot of self-confidence. Another way of interpreting this situation is: "Hey, that must have been a nice joke that they just told themselves".

Little changes in the little voice that you have inside of your head give big changes to the emotions that you feel, to the self-confidence that you have and to the anxiety that you won't have anymore.