So I'll begin with the Gospel portion of this by quoting scriptures that let us know gratitude is not just a good trait to have--it is a commandment.
Leviticus 22:29 - And when ye will offer a sacrifice of thanksgiving unto the , offer at your own will.
Alma 34:38 - That ye contend no more against the Holy Ghost, but that ye receive it, and take upon you the name of Christ; that ye humble yourselves even to the dust, and worship God, in whatsoever place ye may be in, in spirit and in truth; and that ye live in thanksgiving daily, for the many mercies and blessings which he doth bestow upon you.
Doctrine & Covenants 46:7 - But ye are commanded in all things to ask of God, who giveth liberally; and that which the Spirit testifies unto you even so I would that ye should do in all holiness of heart, walking uprightly before me,considering the end of your salvation, doing all things with prayer and thanksgiving, that ye may not be seduced by evil spirits, or doctrines of devils, or the commandments of men; for some are of men, and others of devils.
Doctrine & Covenants 59:21 - And in nothing doth man offend God, or against none is his wrath kindled, save those who confess not his hand in all things, and obey not his commandments.
The last one, to me, is the most direct about gratitude and the Gospel--because it offends our Havenly Father to not acknowledge where all we have comes from.