The following piece addresses the issue of spiritual lethargy. He talks about the part personal sacrifice plays in spiritual growth. I have never heard it said better. 

  "In the mere negative virtue, meaning that which abstains from gross outward wrongs, which commits neither theft, nor cruelty, nor excess, and paces the daily round of usage, there is not necessarily any principle of spiritual growth. The force required to maintain it becomes continually less, as the obstructions are worn down by ceaseless attrition; and the character may hence become simply automatic, performing a series of religious duties with the smallest expenditure of the soul.

To nourish high affections, worthy of a nature that has kindred with the Father of spirits, more than this is needed: positive and creative power, spontaneous and original force, conquering energy of resolve, must be put forth: from the inner soul some central strength must pass upon the active life, to destroy that equilibrium between within and without which makes our days mere self-repetitions, and to give us a progressive history.

There is a connection profound and beautiful between the affectionate and the self-denying character of Christianity.

The voluntary sacrifices feed the involuntary sympathies of virtue: and he that will daily suffer for his duty, and not lay his head to rest till he has renounced some ease, embraced some hardship, in the service of others and of God, shall replenish the fountains of his holiest life; and shall find his soul not settling into the flat and stagnant marsh, but flowing under the most delicious light of heaven above, over the gladdest fields of Providence below.

God will have us surrender without terms; and until then, we are fast prisoners, and not free children in his universe.

So needful is sacrifice to the health and hardihood of conscience, that if the occasions for it do not present themselves spontaneously in our lives, we must create them for ourselves: not reserving to ourselves only those exercises of virtue which are constitutionally pleasant, but on the contrary, esteeming the difficulty of a duty as the reason why we should put our hand to it at once.

He, in short, is no true soldier of the Lord, nor worthy to bear the Christian armor, who in service so high, will not make an hour's forced march of duty every day. So tasked and tested, the inner power, the athletic vigor, of our moral nature, will not waste and die. The perceptions of goodness, beauty, truth, become, when we are thus faithful, singularly clear: there ripens within us the fullest faith in the moral excellence of God; the ties that bind us to him and to his children are drawn more closely round; and in this world we dwell as in the lower mansion of his house, where also the "Father loves us, and makes his abode with us."

  By such practical performance alone, can any genuine love of man be matured in us. Charitable deeds are the true school of learning and kindle our desire to do good to others. We are not to wait, till some descending spirit, uninvoked and unearned enters us and makes the labor of sympathy delightful; but to go and do the deed of mercy, thought it be with reluctant step, with dry and parched spirit, and without the grace of a free charity.

Perhaps we may return with a more genial mind and liberated affections: and if not, we must sooner and the oftener do the act of blessing again, though it be amid self-rebuke and shame, and recoil with no peace upon the soul. He that with patience will become the distributor of sympathy and good deeds to the poor and sad, and ask no portion of the blessing for himself, shall catch the spirit of the divine love at length: those whom he steadfastly benefits he will rejoice in at the end.

  By such practical performance alone, can we dismiss the clouds of doubt and ignoble mistrust, which, really covering our own disordered minds, seem to cast shadows around the Most High, and to blot out the heavens from us." Martineau.