All motivational slogans are a bit **** TBH, or at the very least not particularly “British”… Leave that sort of things to colonial types
I would consider applying Harsh, Demotivational stickers to my bikes with something like this on them:
“Everyone Hates You!”
“Everyone can see the outline of your genitals!”
“Pedal as fast as you like, you’ll never outrun THE SHAME!”
“This Bike makes you look even Fatter!”
” I’m going to punch you in the scrotum!”
As it is my kids keep wanting to put Peppa Pig stickers on all my bikes, I think the contrast of unpleasant personal threats and children’s TV characters would set any bike off nicely, and give any potential thieves real pause for thought…