Joseph Addison (1672-1719) puts it quite nicely this way: "Two persons who have chosen each other out of all the species with a design to be each other's mutual comfort and entertainment have, in that action, bound themselves to be good-humored, affable, discreet, forgiving, patient, and joyful, with respect to each other's frailties and perfections, to the end of their lives."
Of course it isn't always easy because conflicts about ideas, choices and habits arise. Some of these conflicting situations are easy to overlook while others can be very annoying, upsetting, and continual. Some personal mannerisms of one may never suit those of the other, and compromise cannot always be reached. Parting ways might seem inevitable, but often relaxing and rethinking the whole picture can result in a positive turn.
For example, many difficulties in a friendship, including marriage, can be put to the back by the simple act of resignation. By accepting certain personal conditions as permanent, they will somehow become more acceptable. Eventually the conflicting ideas may not be much of an issue, thanks to resignation. This leaves more room for mutual contentment and fondness.
Has the other's point of view been considered earnestly? How about a commitment to doing things that are basically unfavorable if it will improve the relationship? What are the other's favorable traits and conditions that are being overlooked? Nobody has to be perfect!
"If you wished to be loved, love." - Lucius Seneca (3-65)