Our brains are wired to take short cuts, and judgments are a very common yet potentially problematic short cut. As a result, we are often judgmental, and that can lead to anger, sadness, guilt, etc. Mindfulness is a tool to combat judgements.
Compassion can help reduce judgments and make it easier to understand and accept others, even when we don't like what they do or believe. Understanding how the mind works can help you use this simple strategy to increase compassion.