We often don't realize when our thought process is running through a negative filter.
As you practice building awareness of your thoughts, you are able to catch your negative thinking, then work toward a more positive or helpful perspective. (And a more authentic and true perspective, I think.)
This is a great infographic showing types of unhelpful thinking patterns we often experience, but may not often realize.
In my own practice to quash negative thinking, I found it helpful to identify the different types of negative thought patterns.
Infographics are great tools to use when you're trying to make lifestyle and cognitive changes. Pin it up on your fridge or bathroom mirror, set a regular reminder on your phone to take a peek at the PDF. Put it where ever it works for you.
Remember, just because you think it, doesn't mean it's true.