How does one maintain one’s inspiration throughout life? The key is building oneself up spiritually in one’s younger years. The higher one’s level in his youth, the less he will fall later on:
... Concerning your question about where to continue your studies, and in what manner.In my opinion, education of youth, especially education at your age, influences the entire course of one’s life, and one’s independence and firmness depend upon this. This enables every person to withstand the challenges that he may face in life.
We find ourselves in an age of numerous changes, in which it is impossible to predict our lifestyle in several years time. Thus one cannot know how great the challenges one is destined to face in the realm of just, righteous behavior, and in faith and religion.
Therefore every single member of the youth should and must receive religious education to the maximum degree, in order to enable him to overcome any danger that may come, G–d forbid. And even if such an education involves some inconvenience or the like for a certain period of time, of what significance is this when compared with the immunization and extra strength that one only receives through this education, for one’s entire life.
Likkutei Sichos, Vol. 22, p. 387.
If in one maintains a certain religious level to a certain degree, this is only thanks to the fact that in his youth he was on a higher spiritual level. Then although difficulties of life and the struggle for survival and against the environment may have reduced the level of his youth, he remains at least with his level of middle age. It follows that one who is on a lower level in his youth will naturally fall from his level after several years to a level lower than what one would have hoped.
Likkutei Sichos, Vol. 22, p. 386.
Someone once questioned the need for the rigorous schedule and intense atmosphere of Tomchei Temimim. A chossid responded with an analogy from a furnace: If one only wishes to heat up the room where the furnace is, then it need not be heated up so much. But if one wants to heat up the entire house, even the rooms a fair distance away from the furnace, then the furnace must be heated up to the highest temperature possible!