Surround yourself with positive people; put yourself in positive situations. Your associations directly contribute to your mindset.
Have you ever noticed that if you spend too much time with negative people that you start to become negative?
Is there a person that is in your life that you can count on to be negative? Is there someone who always has a negative thing to say? Is there someone who is a complainer?
Social media has created a forum for negativism and complaining. There are groups and places specifically engineered for negativism and contempt. Don’t fall into this trap.
When you spend time with positive, optimistic people your own attitude shifts towards a more positive, optimistic mindset. Purposefully think about the locations – both physical and electronic – that you spend time. Associate with the type of people, in the places, that support your aspirations and goals. 
Like Mark Twain reminds us, “Never argue with stupid people, they will drag you down to their level and then beat you with experience.”