Image from this website talk on papanca
The important thing is to sustain moment to moment awareness of the mind. If you are really caught in mental proliferation, then gather it all together, and contemplate it in terms of being one whole, cut it off right from the start, saying, “All these thoughts, ideas, and imaginings of mine are simply simply thought proliferation and nothing more. It’s all anicca, dukkha, and anatta. None of it is certain at all.”
Discard it right there.