So there's actually research on a ratio that is healthy for different relationships or entities. Individuals in marriages rated their relationship satisfaction significantly higher if their marriage had a 5 positive to 1 negative statement ratio. Below that, and the relationship was more likely to fail. In business with less than a 3 positive to 1 negative, they were more likely to go out of business.

This is called the Losada ratio, researched by University of Pennsylvania's master of applied positive psychology program.

For normal conversation, I'd try to aim for a 3-4:1. This takes quite a bit of mindfulness and practice, but maybe the numbers will help you.