A 38-year-old client reports experiencing frequent, severe tension headaches, especially during stressful periods at work. They also mention that their doctor has noted borderline high blood pressure. The client is highly motivated to find a non-pharmacological treatment and expresses a strong interest in learning how to 'gain more control' over their body's involuntary reactions to stress. Based on this information, propose a suitable therapeutic technique and explain your reasoning, specifically detailing how it would address the client's symptoms and goals.