Sorry to reply for this late,...
Anyways what you said here is almost right.
"when it is "us" who do not cope with such an endurance, because marriage is not one person, but the agreement to live together and to get that oneness few have found out." - there is something missing here,God.
Without Christ no marriage is really a success.
i am learning it first hand,and it's tough sometimes when i try handling the ship during the storm on my own when i am expected to sit with family and Jesus is supposed to handle the steering wheel.In married life when husband and wife Prays and Cries to Jesus,Oneness comes from Him and its in Him.
note:- i don't come in here(in CC) much because i am not giving any funds to run this site here.So am a little ashamed of making use of it freely when i am expected to give some small funding.Any kind of good advice is appreciated.