True positivity starts with the self. How we see ourselves is how we see others and how we see the world.
Accepting your characteristics, your flaws, your history is the first step to knowing your true self. Without being comfortable in your own skin, you will kill any chance of seeing the good in anything because you will always worry about what others think about you. You must have a relationship with yourself first before you can have a loving relationship with everyone else.
It is hard to not make judgments about others. We all do it. I still do it and often, have to be aware my brain is on autopilot and running on a made-up fear that others being different than myself is a bad thing when being different is what makes us special. In order to stop the judgments, start with ending the judgments with yourself. This is not an overnight success but constant practice of self-acceptance and awareness of automated judgments will have you wake up one day seeing the work pay off for you.
A short morning practice:
Start your day accepting one thing about who you are. It can be a personality trait, a physical characteristic, something that happened when you were a kid, a past relationship anything that is part of who you are. Allow yourself to sit with what you chose. Try not to analyze or criticize rather feel comfortable with what you chose.