This beautiful blue flower, which grows throughout France and much of the rest of the planet, has remarkable relaxation properties. These can be obtained by smell (aromatherapy), simply by keeping bunches of dried or fresh lavender around your home. Spraying lavender oil on your pillow to help sleep or putting a drop on your upper lip under your nose will also help you to calm. Lavender oil is also available in capsule form, and this can also be very effective to help you sleep, and to stay calm.
So to paraphrase, "Stay calm and carry Lavender."