Yes, relaxation is the most important factor and I have found that counting slowly while in a hold down works wonders in relaxation. It is amazing how fast you think time goes, but, if you count you realize that you have only been down a fraction of what you know you can do. I was in a breath holding "contest" last time I was in El Sal and the first guy came up saying that he thought he had been down 40 seconds. I had been counting and knew he had only been down 15 seconds. I kept on counting and stayed down 2 min 15 sec and when I surfaced I felt like I could have been down another minute. I only "train" infrequently and it helps, but, knowing how long I can hold my breath AND knowing how long I have been down helps a lot in relaxing.