It's absolutely magic!
The other day I was in the nets with a friend. I was attempting to bowl off-spin and failing miserably. About half of my balls were waist-high, legside full tosses, with the rest being predominantly short-pitched garbage and legside wides with the very occasional ball landing in a good area. It was frustrating and disheartening.
Today we were in the nets again. I began bowling, and the same thing happened. Waist-high full tosses and more tripe. But then I decided to implement something which had previously given me success in bowling of the ten-pin variety. As I walked in to bowl, I not only looked at where I wanted the ball to land but also visualised it landing there. I also repeated to myself "I give it flight and bowl around off stump, I give it flight and bowl around off stump...". As by magic, I started landing it better. There were still some short balls and legside wides, but practically no waist-high full tosses and drivel like that. I would say that I went from landing 1/10 balls in a decent area to about 7/10 without making any conscious change to my technique. Obviously I still need to work on my consistency, but that will come with practice.
If anybody has never tried visualisation and repeating positive affirmations in your head, you really need to give it a go. I cannot explain how it works, but it does!