Helaman 6

17 For behold, the Lord had blessed them so long with the riches of the world that they had not been stirred up to anger, to wars, nor to bloodshed; therefore they began to set their hearts upon their riches; yea, they began to seek to get gain that they might be lifted up one above another

When the Lord blesses us with peace and prosperity, we sometimes set our hearts on the things of the world. An attitude of gratitude prevents that. If we constantly remember from whence those blessings come, we can remain humble and use the blessings we have been given to bless the lives of others. If we set our hearts on worldly things, our faith dwindles and we are left to our own devices. On the other hand, if we seek the Lord humbly and keep his commandments, he blesses us beyond measure with "the peace of God, which passeth all understanding." This happens as we are willing to believe.

34 And thus we see that the Nephites did begin to dwindle in unbelief, and grow in wickedness and abominations, while the Lamanites began to grow exceedingly in the knowledge of their God; yea, they did begin to keep his statutes and commandments, and to walk in truth and uprightness before him.

35 And thus we see that the Spirit of the Lord began to withdraw from the Nephites, because of the wickedness and the hardness of their hearts.

36 And thus we see that the Lord began to pour out his Spirit upon the Lamanites, because of their easiness and willingness to believe in his words.