The essential oil that is best for the heart is lavender.
It helps to calm the mind, restore the spirit and bring peace. Lavender is the perfect essential oil to rub on point Heart 7 (located at the wrist, in line with the pinkie finger), make sure to apply it on the point and up and down the meridian line.
As it's summer, take advantage of any fresh lavender you can get your hands on too and place in your bedroom or kitchen.