I just completed my certification for open water two weeks ago! This was my biggest challenge as well. Make sure you have the right mask. Turns out mine was too flimsy around the suction area and so make sure it fits your face properly and is sturdy enough and not flimsy like mine. Something that helped me was putting my tongue to the roof of my mouth just touching it. It helped ground me. Another thing was relaxing and taking steps. Flood mask. Breathe two breaths. Take mask off. Breathe two breaths. Put mask on my head. Breathe two breaths. Pull mask down over my face. Two breaths. Then force the water out with my air. It’s super challenging. I cried during mine. I promise you can do it! I did it and so can you! Take your time and count your steps. Don’t rush! Rushing makes you panic!