At the beginning of your meditation first focus on your fontanelle bone, on top of your head. It makes it easier if you put a hand on your head and press down slightly, massaging the scalp in a clockwise direction.
Then start with a simple breathing exercise.
Breath in, hold the breath, breath out, hold the breath
When you feel emotionally up-set or stressed try to dissolve this emotions with this breathing exercise. Combine the emotion with your breathing, let the emotion go out with your breathing.
Continue with this breathing exercise in your own rhythm until you feel calm inside.