We do not obtain fulfillment directly, but indirectly. Do not look so much at how your spouse will make you happy. Look instead at how you can give yourself away to each other. There is a big difference between a contract and a covenant. In a contract, people exchange goods and services.
Every sale is a kind of contract.
In a covenant, however, people do not exchange things. They give themselves . Marriage is a covenant. When Christ died on the cross, He established an everlasting covenant with us. He gives us Himself in Holy Communion, and we give ourselves back to Him in obedience and love.