Your thoughts defines your personality. The Bible says
For as he thinketh in his heart, so is he: Proverbs 23:7 King James Version (KJV)
The state of our lives is determined by the character of our thoughts. Positive thoughts will birth joy, happiness, love and fulfillment. Negative thoughts on the other hand; depression, hatred, anger and bitterness.
The cycle
We access information primarily from what we hear and what we see. The information you feed on generates thoughts in your mind. If, for example, you read a lot about business, you would almost always be thinking in that direction. The same applies to other aspects of life like music, politics, and academia. The more you read about music, the more you would have thoughts about music.
Your thoughts will alter you actions. A typical example will be your response if you get to know that the plane your going to travel with did not successfully pass all the safety checks. There is no way you would go on that plane! The reason is you got the information that sparked a thought that you could die if you boarded that plane and that affected you action. If you did not know, you would not not board the plane.
Actions when practiced for a long time will form a habit. Like having a habit of always making sure your flight is safe. And habits will define your character. People will now describe you as someone who takes safety seriously.
In summary, the information you feed on, controls your actions. Your actions will develop into habits and habits, character. It all starts from the mind. This is the reason why the Bible says
Finally, brethren, whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and if there is anything praiseworthy—meditate on these things. Philippians 4:8 New King James Version (NKJV)
If you are having problems with negative thoughts, all you have to do is to check the information you feed on. If you always have thoughts of fear for example; it could be because of the friends you have hang out with talk about things that put fear in you. It could be the movies you watch. Horror movies can put fear in you. You may find it difficult to walk alone in the dark after a watching a horror movie. So you have to consciously choose the information you are going to put inside you and it will make all the difference. The standard for choosing the information is in Philippians 4:8. Is the information pure? Is it noble? Is it just? Is it lovely? Is it of good report? Is it virtuous? or is it praiseworthy?
I hope this post help you in living a life free of negative thoughts. Let me know your thoughts on the subject and you can leave any question you may have in the comments below.