Practice your "No" in front of a mirror using three postures: seated with spine straight, standing with feet shoulder-width apart, and in your power pose. Keep your voice steady, maintain eye contact with yourself, and avoid apologizing or explaining. Remember: your boundaries are not just suggestions—they are vital shields protecting your healing nervous system from retraumatization. Start with "No, that doesn't work for me" before advancing to more challenging statements like "No, I won't accept that behavior anymore."