Be conscious of the high-strung person's mood and energy when you are around him. Recognize his body language and his tone of voice. Note how he reacts to certain situations and the people around him. Know what to expect when you are around this person, so that you can prepare yourself to deal with his behavior, suggests Melissa Galea, a behavioral health psychology researcher, in “Second-Hand Stress” on the website Alive.

Pay attention to your body and mind to regain control. When you are around a high-strung person, be conscious of your own emotions and physical reactions. Do your breaths get shallow? Does your heart rate increase? Be aware of any tension or heaviness in your chest. Once you notice your body and mind getting into a negative state, consciously refuse her influence, says psychology professor Sherianna Boyle in “The Everything Parent’s Guide to Overcoming Childhood Anxiety: Professional Advice to Help Your Child Feel Confident, Resilient, and Secure.” Stay in the present moment and focus on gaining control of your breaths and talking yourself out of the negative mindset.

Keep your tone and body language in check when communicating with him. Remain calm and rational. Just as nervousness and stress can be contagious, so can calmness and collectedness. Act in control and you will appear in control, says psychologist Christian Jarrett in “The 4 Ways You Can Use Body Language To Influence Success” on the website 99u. Open up your body by uncrossing your arms and standing tall. Speaking in a soft, relaxed voice may also get the person to mirror your calmness and ease his anxieties.

Be sympathetic and reassuring, but don’t coddle her. Listen to her complaints and worries. Respond with a calm voice and compassionate words. While you want to be there for her, it’s important not to do everything for her, just to calm her down. Encourage her to overcome her own emotions. High-strung people need to be assured that they are the ones who are ultimately in control of their situation, according to psychologist George Simon in response to a question on the website Ask the Psychologist.

Limit how much he can depend on you. If the other person’s high-strung energy is stressing you out, don’t be afraid to set boundaries. Reassure him that you know he’s not doing it on purpose and that you want to help him, but you can’t do that properly if his mood is affecting yours. Emphasize that you care about him and have faith that he can deal with certain situations on his own, without your assistance or constant reassurance. You may have to enforce these boundaries gradually.