One thing that can cause us to be judgmental is not listening when we come to Jesus. In John 8 the Pharisees are bringing a woman caught in adultery before Jesus to try to trick Him. In verse 2 the bible says that Jesus was in the temple courts and the people were gathered around listening to Him teach. The Pharisees were clearly not there to listen to Jesus. Had they been listening at any point in Jesus ministry they would have already known the answer to their question. They did not want to hear what Jesus had to say on that subject or any other because it might cause them to have to do something different. It would definitely cause them to have to stop being judgmental. That is really the problem when we are not listening. We do stuff or say stuff or don't do stuff because that is what we feel like we need to do for whatever reason not because Jesus told us to. That is in no way putting your faith and trust in Jesus. That is putting your faith in yourself and what you think is best. When we come to Jesus and we have our own agenda already laid out, we are probably not going to be listening to Him. Not listening to Jesus will cause you to become a person who Judges others. When you continue to judge others, you will continue to not listen to Jesus.
However, if we choose to listen to Jesus we will walk in the love, grace, and forgiveness that He continually walks in with each of us. That is an excellent way to allow your faith to affect what you do. Let's stop being people who are judgmental and start being people who listen to Jesus.