Stress reducers are 

Social interaction and support (more here);

Committed romance;

Arguing “a little”;

Laughter (more here and here);

Living in a calming environment;

Taking time for ourselves (more here);

Spending time with a dog;

Listening to music, especially bland music;

Some smartphone apps;

Managing our expectations;

Finding the positive in unwanted occurrences;

Meditation (more here and here), especially transcendental meditation, yoga, deep breathing (more here), or pausing and taking one deep breath before a stressful activity;

Acupuncture;

Eating healthy foods, often;

Eating foods seasoned with saffron and foods containing omega-3 fatty acids (more here), a complex of B vitamins, and vitamin C;

Eating chocolate and unrefined carbohydrates and drinking tea;

Sniffing apple, coconut (more here), lavender, or peppermint;

Taking calcium and magnesium, kavakava, passion flower tincture or extract, valerian root, St. John's Wort; and

Exercising (more here and here, especially outdoors and with high intensity), or just tightening muscles or shaking fingers and hands.