Open that photo of your ex-girlfriend again, that shows her breasts. This time you may look at them. They should of course be clothed, seeing them naked is off limits to you. Think about her new boyfriend taking off your ex-girlfriend's top, undoing her bra, and grabbing her exposed boobs. Then say to her, while thinking of her boobs being fondled by her new boyfriend:
"<Ex's name>, your boobs are off limits to me, please enjoy all the sexual tension between you and <new bf's name>, while he plays with your boobs."
repeat 3 times / one stroke per word / 1 edge after the 3rd repetition