The Parable of the Prodigal Son
No matter how far out of the match you think you are, there's always hope for a comeback. (Just look at Novak Djokavic.)
In tennis, a strange phenomenon occurs, all too often, to players after they win the first set. They abruptly tank around the middle of the second! They just lose their focus. With decreased energy and droopy body language, they still go after these big winners, but now—nothing is working for them. It's crazy that they can't figure it out! Their fundamentals are clearly lacking; they no longer reach for their serves, their groundstrokes are flatfooted, everything just seem lazy.
In life, a bizarre corollary tragically exists. It is all-too-common for stalwart members of the Church to spiritually let down around the "mid-second-set." Morals and standards relax. Fundamental behaviors (e.g., scripture reading, daily prayer, temple attendance, etc.), which were once routine, have slipped. One's "game" begins to suffer, and for the life of the individual, they can't figure out why.
If you have fallen victim to this common trap, or know someone who has, remember this—God is able to reach down, reclaim you, and lift you (and/or them) up from the most profound of depths in the very moment you reach out to Him (Alma 36:17-21). You've just got to rally your energy, and try.
"My dear brothers and sisters, don’t get discouraged if you stumble at times. Don’t feel downcast or despair if you don’t feel worthy to be a disciple of Christ at all times. The first step to walking in righteousness is simply to try. We must try to believe. Try to learn of God: read the scriptures; study the words of His latter-day prophets; choose to listen to the Father, and do the things He asks of us. Try and keep on trying until that which seems difficult, becomes possible—and that which seems only possible, becomes habit and a real part of you."
—Dieter F. Uchtdorf, The Love of God, LDS General Conference, October 2009