Who or what do you think influences how you think, family, friends, the media?
Your thoughts are influenced by whatever you put your attention on. So whatever you expose yourself to on a daily basis will overtime drive your thinking, whether you admit it or not.
Your brain absorbs so much information in a subliminal manner and you’re often unaware of all the information being stored. That’s why advertisers keep showing and playing the same ads over and over, because they know that even though you think you’re ignoring them, your brain is in fact storing them.
There will be times when you cannot avoid information or stories that lead you to think about things that bring you down. However, if you want to experience strong, positive uplifting thoughts then you should make a conscious effort to expose your mind to information that will help you lead such a life.