It's basically asking you to explain a time in your life when you came up with different reasons for an event and contemplating them vs. going with your first thought and running with it.

An example of my own I can give is when "in the past" my husband was late from work and I would automatically assume he was cheating on me and all of my behaviors related to that thought with no exception. "that is when I did NOT act dialectically".
On the other hand when I DID act dialectically is when my husband was late from work and I would weigh out options for why like 1. he had extra paperwork after work, 2. He got stuck in traffic, 3. He had to stop off at the store on his way home, etc..

Hope that helps you out some :-)