A trigger can occur using any of your senses. An item that you wear, or hold, can put in motion the memory of what you want to focus on currently, A scent can transport you, to a known time. A sound can remind you.
Think of the special occasions, the ceremonies, something as simple as going to the theatre, they all have a scent that you instantly relate to that occasion. In the same way, by creating an atmosphere, that perhaps has a constant, can assist in propelling you in to that place quickly. In this way at your time, in your place you can create the desired surroundings, for example for relaxation, meditation or tranquility.
What trigger suits you?