When a man shuns effort, he is in no position to resist temptation

"When a man shuns effort, he is in no position to resist temptation. So, through all the ages, idleness has been known as the parent of all the vices."

(David Starr Jordan, The Strength of Being Clean [New York and Boston: H.M. Caldwell Co., 1900], pp. 18–19.), as quoted in "The Nobility of Man in Choosing Good over Evil" by Elder Alvin R. Dyer, Assistant to the Council of the Twelve, General Conference, October 1971, https://www.churchofjesuschrist.org/study/general-conference/1971/10/the-nobility-of-man-in-choosing-good-over-evil?lang=eng 

When we lose the Spirit, it's easy to think we never had a testimony

"...a testimony is nothing more or less than the Holy Ghost bearing witness to our soul of the truthfulness of the gospel and of the restored Church. When we fail to pray and study the scriptures, the influence of the Spirit in our life is weakened, lowering our resistance to temptation. When we sin and become unclean, we lose the companionship of the Holy Ghost altogether. Without the ongoing witness of the Spirit, we can easily begin to think we don’t have a testimony and maybe never did.

"Our testimony needs to be continually nourished. That nourishment comes from personal prayer, daily scripture study—particularly the Book of Mormon—and serving in the Church throughout our life."

- Elder C. Scott Grow, Of the Seventy, "Prophetic Principles of Faithfulness," Ensign, January 2017, p. 16

https://www.lds.org/ensign/2017/01/young-adults/prophetic-principles-of-faithfulness?lang=eng

Daily scripture study imparts strength to avoid temptation

“If you immerse yourself in the scriptures each day of your life, you will have strength to resist serious transgression...”

- Elder Daniel L. Johnson, of the Seventy, “Hold Fast to the Rod,” Ensign, February 2016, p. 61

https://www.lds.org/ensign/2016/02/hold-fast-to-the-rod?lang=eng

Blessings of doing family history

“Never forget that family history—and the temple ordinances enabled by it—is an essential part of the work of salvation and that participation in this sacred work for the dead blesses the lives of the living. It strengthens our faith in and commitment to the gospel, helps us resist temptation, draws our families closer together, and strengthens our wards and stakes.”

...

“As an Apostle of the Lord Jesus Christ, I promise that if you look beyond the bonds of time and mortality and help those who cannot help themselves, you will be blessed with more closeness and joy in your family and with the divine protection afforded those who are faithful in His service.”

- Elder Quentin L. Cook, of the Quorum of the Twelve Apostles, “The Joy of Family History Work,” Ensign, February 2016, p. 29 and 33

https://www.lds.org/ensign/2016/02/the-joy-of-family-history-work?lang=eng

Service lessens power of temptations

“Fill your life with service to others. As you lose your life in the service of Father in Heaven's children, Satan's temptations lose power in your life.”

- Elder Richard G. Scott, of the Quorum of the Twelve Apostles, “Personal Strength through the Atonement of Jesus Christ,” October 2013 General Conference, https://www.lds.org/general-conference/2013/10/personal-strength-through-the-atonement-of-jesus-christ?lang=eng

FHE helps us withstand temptations

"We cannot afford to neglect this heaven-inspired program [family home evening]. It can bring spiritual growth to each member of the family, helping him or her to withstand the temptations which are everywhere. The lessons learned in the home are those that last the longest."

- Thomas S. Monson, First Counselor in the First Presidency, "Constant Truths for Changing Times," General Conference, April 2005

Service lessens temptation's power

"Fill your life with service to others. As you lose your life in the service of Father in Heaven’s children, Satan’s temptations lose power in your life."

- Richard G. Scott, of the Quorum of the Twelve Apostles, "Personal Strength through the Atonement of Jesus Christ," General Conference, Oct 2013

https://www.lds.org/general-conference/2013/10/personal-strength-through-the-atonement-of-jesus-christ?lang=eng

“As you faithfully plan and hold quality family home evenings, you will gain strength to withstand the temptations of the world and will receive many blessings which will help qualify you to enjoy your families through eternity in the Celestial Kingdom.”

- The First Presidency, Family Home Evening (1978), 2. As quoted in "Family Home Evening for Two," Ensign, Dec 2004
http://www.lds.org/ensign/2004/12/family-home-evening-for-two?lang=eng#footnote1-24912_000_015

Lucifer opposes the plan of happiness

"The single purpose of Lucifer is to oppose the great plan of happiness, to corrupt the purest, most beautiful and appealing experiences of life: romance, love, marriage, and parenthood."

- Elder Boyd K. Packer, Of the Quorum of the Twelve Apostles, "For Time and All Eternity," General Conference, Oct 1993
http://www.lds.org/general-conference/1993/10/for-time-and-all-eternity?lang=eng#12-

If you would be happy, resist temptation

“I wish I could say to every young man in this Church, that if you would be successful, if you would be happy, if you would conserve your strength, intellectual, physical, and spiritual, you will resist temptation to indulge your appetites and your passions.”

- David O. McKay, from The Improvement Era, 48:310, as quoted in "Dandy," New Era, Apr 2003, p. 10
http://www.lds.org/new-era/2003/04/dandy?lang=eng

If you cross to the devil's side of the line you cannot think properly

"There is a line of demarcation, well defined, between the Lord’s territory and the devil’s. If you will stay on the Lord’s side of the line, you will be under his influence and will have no desire to do wrong; but if you cross to the devil’s side of the line one inch, you are in the tempter’s power, and if he is successful, you will not be able to think or even reason properly, because you will have lost the Spirit of the Lord.”

- George Albert Smith, as quoted by Elder David B. Haight Of the Quorum of the Twelve Apostles in "Personal Morality," General Conference, Oct 1984
http://www.lds.org/general-conference/1984/10/personal-morality?lang=eng