A caveat with the singing - sometimes you have to pay attention to what's coming out your mouth. I was listening to Doug Anthony Allstars on my way to the stables and found myself singing I **** Dogs while cantering round the school. Which was also being used by a ten-year-old...
Can't quote but KatPT has it exactly right. Breathe through your stomach not your your chest. It relaxes you more and being less tense will relax your horse more. Also '1-2-3 in 1-2-3 out' (think of it like 3 time in music) in time with your horses canter.
Have someone else in the arena with you and have a conversation? When jumping I have the habit of looking down so my instructor stands at the other side of the jump and makes me count fingers and shout out the number.
