The gospel in the LDS church and its covenants, oaths, and laws (as said above) can bring happiness, eternal joy, and lasting relationships, if applied. We, as missionaries, try to bring this to those that might not have these blessings in their lives currently. D&C 131:2-4 says, " 2 And in order to obtain the highest, a man must enter into this order of the priesthood [meaning the new and everlasting covenant of marriage];
4 He may enter into the other, but that is the end of his kingdom; he cannot have an increase.
5 The more sure word of prophecy means a man’s knowing that he is sealed up unto eternal life, by revelation and the spirit of prophecy, through the power of the Holy Priesthood.
Marriage is the most important ordinance in the LDS church and can only be participated in by two worthy individuals, a man and a woman, that love each other. The relationship can only be valid if the Holy Spirit blesses it, that's if the two individuals live worthy to each other.
The sealing room that couples get married in, look like this. This is in the Payson, Utah Temple.