Hi there -- I had this problem, but in reverse. I had a critical judgmental thought about the people I saw on the streets.

Here is what a spiritual mentor taught me to do: When I noticed the negative thought, I would mentally say, "Who is your parent? You don't belong here," disowning the thought as my own. Then I would replace it with a kind thought. My understanding of our mental processes is that we can switch from one thought to another rapidly, but we cannot hold two thoughts at the same time.

I had to be consistent about this for a long time -- almost a year. I felt so happy the first time a spontaneous nice thought about two people getting out of a car. They were a bit overweight, but my first thought was, "Look how in love they are. The treat each other with such respect."

Don't give up. You can change your thoughts.