From the book: Vivid Awareness - The Mind Instructions of Khenpo Gangshar, here are some of the clearest meditation instructions I have come across recently:
Keep your body straight, refrain from talking, open your mouth slightly, and let your breath flow naturally.
Don't pursue the past and don't invite the future. Simply rest naturally in the naked ordinary mind of the immediate present without trying to correct or "replace" it. If you rest like that, your mind-essence is clear and expansive, vivid and naked, without any concerns about thought or recollection, joy or pain. That is awareness (rigpa).
At the same time, there is no thought of, "Sights and sounds are out there". Everything appears unceasingly. There is also no thought of, "The perceiver, the six types of consciousness, is within". Clear and non-conceptual naked awareness is unceasing.
While in that state, your body is left to itself without fabrication, free and easy. This mind essence is the nature of sentient beings.
The part "Don't pursue the past and don't invite the future" in particular seemed to help me a lot to instantly quieten my mind whenever i recalled it, after recently having a negative experience that created turbulent thoughts for the night.