In a long term relationship, I think of there being at least five legs to the table:
safety: financial and physical, can you meet your needs together, are you healthy for each other?
sexual: well, you know what that is.
friendship: do you entertain and interest each other when you are not having sex?
social: do you make a unit that reinforces your standing in the context of work, family, friends?
domestic: is daily life more pleasant, do you enjoy and provide each other with food, comfortable bedding, other everyday human comforts and considerations?
With all five legs you can dance on the table like a crazy fool, and it will still stand. It will stand even with three legs, but then you will have to be more careful not to tip it over.