I like the idea of a curse that makes you make a hard choice. Like you can't masturbate until you've done something. Maybe for a man, you can't masturbate until you've undressed in front of another man, say in a locker room, while wearing panties. In this case, for each time you want to masturbate, a stranger has to see that you are wearing panties. If you can't think of a safe way of doing it, then you just can't masturbate.
Or maybe it's a curse you can cancel yourself by just doing something once. Like you can't masturbate until you've told a man that you've sucked a guy off. You can make up any circumstances you want and lie all you want, but you have to tell a man you've sucked and swallowed, or you can't masturbate. Once you've told, you're normal again.
Are these little challenges too tame? I like the aspect that they might lead to getting you screwed, but you'd also have to be very careful. That's why you have a choice.