or: think of how commercials work!
you might have heard the same commercial several times a day, and this is how they "touch" and influence your subconcious mind - even if you don't listen to them.
so if you want to change your suconcious mind you have to repeat the new thought like a mantra. just repeat it.
an example:
long times of my life i thought i couldn't sleep. someday i thought i was wrong thinking this way. so i started thinking (and saying) i can sleep. i can sleep. i can sleep. i can sleep. i can sleep. i can sleep. i can sleep. i can sleep. i can sleep .......
and what happened? yepp: i could finally sleep - like a baby!!!
it took me "only" three days before it worked
greetings and good luck
bleep