The biggest success-factor for me in using it was - the type of mask.

A full mouth/nose mask (ala "fighter-pilot-mode") was useless, incredibly constricting and confining - I ended-up always removing it after a couple hours of fitful sleep.

Moving to a "nasal pillow" mask made all the difference - I slept the entire night through the first night - and ever since. While some people need a "chin strap" to keep their mouth closed, I found that I did that automatically.