If you're looking for the motivation to carry on, I suggest the 1946 classic 'Man's Search for Meaning', written by Nazi concentration camp survivor Victor E. Frankl.
Surviving the darkest experiences man will ever endure, Frankl found the will to move forward when all hope could have easily evaporated. Immersed in the suffering of Auschwitz and other camps, Frankl found strength can be derived - even in the most dire circumstances - when one has purpose and meaning.
If you don't want to read the book in its entirety, I suggest the following 10 excerpts:
1) "Everything can be taken from a man but one thing: the last of the human freedoms-to choose one's attitude in any given set of circumstances, to choose one's own way."
2) "Don't aim at success. The more you aim at it and make it a target, the more you are going to miss it. For success, like happiness, cannot be pursued; it must ensue, and it only does so as the unintended side effect of one's personal dedication to a cause greater than oneself or as the by-product of one's surrender to a person other than oneself. Happiness must happen, and the same holds for success: you have to let it happen by not caring about it. I want you to listen to what your conscience commands you to do and go on to carry it out to the best of your knowledge. Then you will live to see that in the long-run-in the long-run, I say!-success will follow you precisely because you had forgotten to think about it"
3) "A man who becomes conscious of the responsibility he bears toward a human being who affectionately waits for him, or to an unfinished work, will never be able to throw away his life. He knows the "why" for his existence, and will be able to bear almost any "how"."
4) "Love is the only way to grasp another human being in the innermost core of his personality. No one can become fully aware of the very essence of another human being unless he loves him. By his love he is enabled to see the essential traits and features in the beloved person; and even more, he sees that which is potential in him, which is not yet actualized but yet ought to be actualized. Furthermore, by his love, the loving person enables the beloved person to actualize these potentialities. By making him aware of what he can be and of what he should become, he makes these potentialities come true."
5) "It did not really matter what we expected from life, but rather what life expected from us. We needed to stop asking about the meaning of life, and instead to think of ourselves as those who were being questioned by life-daily and hourly. Our answer must consist, not in talk and meditation, but in right action and in right conduct. Life ultimately means taking the responsibility to find the right answer to its problems and to fulfill the tasks which it constantly sets for each individual."
6) "For the first time in my life I saw the truth as it is set into song by so many poets, proclaimed as the final wisdom by so many thinkers. The truth - that Love is the ultimate and highest goal to which man can aspire. Then I grasped the meaning of the greatest secret that human poetry and human thought and belief have to impart: The salvation of man is through love and in love."
7) "A human being is not one thing among others; things determine each other, but man is ultimately self-determining. What he becomes - within the limits of endowment and environment- he has made out of himself. In the concentration camps, for example, in this living laboratory and on this testing ground, we watched and witnessed some of our comrades behave like swine while others behaved like saints. Man has both potentialities within himself; which one is actualized depends on decisions but not on conditions."
8) "What is demanded of man is not, as some existential philosophers teach, to endure the meaninglessness of life, but rather to bear his incapacity to grasp its unconditional meaningfulness in rational terms."
9) "Everyone has his own specific vocation or mission in life; everyone must carry out a concrete assignment that demands fulfillment. Therein he cannot be replaced, nor can his life be repeated. Thus, everyone's task is unique as is his specific opportunity to implement it."
10) "When we are no longer able to change a situation, we are challenged to change ourselves."