For a marriage to last, what are the 3 most important things needed?

1) Trust. Trust is the foundation of any relationship and a marriage can't possibly thrive in a climate of distrust. 2) Space. Couples can't possibly spend all their free time together. They need to socialise and interact with other people. 3) Effort. A marriage is no different from a car. Without regular maintenance and servicing, it's bound to breakdown. Likewise, couples need to put that occasional extra bit of effort to do nice things for each other. And on regular days, there should be effort to be fully present, giving your partner undivided attention, away from the t.v. and gadgets. And of course, make the effort to have sex. A lot of it ;)