Magnesium and other minerals are critical for the body to physically relax, quite in particular the muscles. When the body is stressed and producing adrenaline, each unit of adrenaline that is made utilises extra magnesium. This can lead to the muscles not having enough enough for sufficient relaxation.
Magnesium is quite easy to find in women's multi-vitamin capsules, found predominantly in green leafy vegetables, nuts and seeds. Some people's sleep and energy improve by taking a magnesium supplement.