The possibility that someone begins sexual relations unwillingly, but is drawn into it during the act against their will: Ketuvot 51b
A woman will accept her husband being away longer, even reducing onah, if it will result in income, but not if it is just for him to pursue his own mitzvot: Ketuvot 62a [see Rashi שאני התם] and Ketuvot 62b [see Tosafot רוצה]
People are able to wait for sexual relations when they know that what they want is within their grasp, even if they cannot use it now [pat b'salo פת בסלו]: Ketuvot 62a-b, 63b
