What you spend your attention on determines what you think. See, for example, the difference in media sources people consume, depending on their political opinion. What you watch, what you listen to, what you read, etc. will all determine what you think.
Think about this:
It's easy to spot a red car when you are always thinking of a red car.
It's easy to spot opportunity when you are always thinking of solutions.
It's easy to spot reasons to be mad when you are always angry.
If we agree that there's a clear connection between what you consume and what you think, then let's go deeper. There's one thing you can control in the chain of attention -> thoughts. You can control what you give your attention to.
Now think about this:
Beware of your thoughts, for they become your words.
Beware of your words, for they become your actions.
Beware of your actions, for they become you.
If you control what you give your attention to, you can influence how you think, which will influence how you act, and ultimately influence who you become. Think of it as an opportunity to have more control over your life.
Pay attention to where you spend attention.