For everyone who exalts himself will be humbled, and he who humbles himself will be exalted. Marriage is death to independent living . No longer do either one of you have a life all your own. Whatever either one of you do, it affects the other. This goes along with no. 2 above.
Selfishness is a sign of immaturity, of being unwilling to speak death to self.
It is a sign of a hard heart. But it was not this way from the beginning. Set it in your hearts and minds that you two have no option but to stick it out and grow old together . There is no other alternative. Marriage is a covenant, not a contract.