Chasidut do Joela 3:2

This is to say that the Mishnah says (Avot 5:21), "Forty [is the age] for understanding, Fifty [is the age] for [giving] counsel." That means that the life of a person is divided into seasons - when he is forty, his mind will be fit for understanding; and when ten more years are added to him, he will reach a different season, that of counsel. And this is not only the case with the seasons of forty and fifty. Rather every number of five or ten years of a person's life differs with regard to their season. For that which the season of young adulthood is fit, later seasons - and even the season of old age - will not be fit. And for that which the seasons of old age and hoary-headedness are fit, the seasons before them will not be fit. And please note this wonder: That when the prophet announced the word of God (Joel 3:1), "After that, I will pour out My spirit on all flesh; your sons and daughters shall prophesy" - he then also distinguished and said, "your old men shall dream dreams, and your young men shall see visions." The sight of the old men will be in a dream, but that of the young men will be in a vision. It is not that we are coming now to explain the difference between the sight of a dream and the sight of a vision. Nevertheless, there is a difference, and the prophet divided them according to their seasons - the young men in their season and the old men in their season. It should be understood that this verse is not relating to God's prophets, who were above their bodies; above time and all of the world. So the level that a prophet would reach in his prophecy, he would reach during any of his seasons, nor was it subject to any season. Rather this verse is speaking about the whole Jewish people, as it is stated (Joel 3:2), "Even upon the slaves and the maidservants, etc., will I pour out My spirit." And the entire people - even in their greatness - is subject to the seasons. This means to say that a person is divided into seasons also in his service of God, and that he is fit for something different in each one of them. For example, there are the seasons of youth, in which a person is more fit to enthuse; and there are the seasons of older age, in which a person is more fit to delight in the pleasantness of the Supernal One. There are seasons when if one does not enthuse, he feels nothing; and there are seasons that even at the time when he is not enthusing, he feels the delightfulness and sweetness from even every simple thing, and even from every letter in the Torah or prayer which he says. There are seasons in which his enthusiasm - like any part of his divine service - begins in his brain, by his delving with his mind; and there are those in which it is more fit to begin in the heart, etc. Hence if a man rises in his youth to serve God through the ways of Chassidut and to bring out all that for which his spirit is fit [in the various seasons] for divine service, he will fix all of them in himself. And at the time of his old age, his service will be a type of crowning glory within which all the shades and faces of the various seasons will be seen. However if he delays getting used to it - even if he toils at it [later] - he will be lacking his seasons that he missed.