Turn negative thoughts into positive ones.
Negative thoughts can be very self-destructing, it's true that how we think is who we are.
Before I go on any further, let's take a quick test
Close your eyes and count slowly to 10, while counting concentrate on listening to numbers.
What did that prove?
While you were counting, what else were you thinking about? Unless you're different from most people answer would be, "I only thought of numbers".
Our minds can only think of one thing at a time, so next time a self doubt or a negative thought pops into your mind, then quickly think of something positive, in other words, change conversation in your head and this will change negative thoughts in your mind.