D&C 124

Some of the saints believe that if they can just get married and sealed in the temple, that all is done.

Of temple covenants and ordinances, the Lord said that if they -

"....do not do the things that I say, I will not perform the oath which I make unto you, neither fulfil the promises which ye expect at my hands, saith the Lord.
48 For instead of blessings, ye, by your own works, bring cursings, wrath, indignation, and judgments upon your own heads, by your follies, and by all your abominations, which you practice before me, saith the Lord."  (Doctrine and Covenants 124:47–48)

For the Lord has declared that He will not be mocked.