well we have only been together for about a year but have only had one real argument. What works for us is love, trust, communication and understanding for starters.
Lots of coitus, lots and lots, of coitus.
Trust, hope, shared experience and good sex.
Communication, and Honesty it's worked for us for 25 years.
The fact that it is love. If it needed anything else i would have got over it by now.