Translated by Ralph Anzarouth and an anonymous friend
Alacrity and insight:
Alacrity is the capability and insight to anticipate events which could materialize and to foresee the results of all one's actions.
Rabbi Shlomo ibn Gevirol of blessed memory wrote that it belongs to the sanguine nature and it is more often found when the spirit is free from bad traits and there is no worry to confuse it; it is proper that man should employ it in all his affairs in his pursuit of wisdom and faith and all of his essential needs.
See and understand the trait of alacrity in the ant, which in the summer days when it sees that the time is ripe it hurries to prepare food provisions towards the autumn and it thinks forward to the period when it will not find what it wants. Accordingly, it scouts and collects grain and conceals it in order that it will help and feed it in the winter days. From this, King Solomon said (Proverbs 6, 6-8): "Go to the ant, you lazy man, observe its ways and gain wisdom. It has no master […]. It will prepare its food in the summer etc. ". He further said (ibid. 10, 4): "The hand of the industrious person will bring prosperity". He also said (Eccl. 2, 14): "The wise man has his eyes in his head1."
Our Sages of blessed memory said in Pirkei Avot (Ethics of the Fathers 2, 10): "Who is wise? The one who thinks ahead". Tullius says: "It is not fitting for a wise man to say 'it did not occur to me that this would happen to me', since if he had been wise rather than worry he should have been hopeful2. Rather than sigh, he would think". Priscianus said: "The wise man's heart is like a ship: when it sinks several people will drown with it". Aristotle said: "The person who thinks that luck will bring good or bad fortune is a fool, since it is wisdom which brings good and folly which brings bad, and when actions are carried out in the proper manner they testify that they have been properly planned". Biacco said: "The key to true confidence is thorough forethought; and the person who thinks sparingly will make many mistakes". Alexander said: "Night was created to consider the deeds of the day3." Seneca said: "It is easier to deal with issues in their initial stages rather than in their latter stages; since, as long as the grass is still pliant, it is easy to uproot, but once it firmly takes roots this becomes very difficult". Cato said: "Always think ahead about what could happen, since the ailment which is foreseen is more easily cured".
[King] Solomon said (Proverbs 11, 14): "Rescue results from abundant reflection".
Aristotle [also] said: "Take your time while taking advice and act quickly on matters on which you have already fully consulted". Theophrastus said: "Nothing good endures without alacrity". Someone else said: "Flowing water will not become toxic." Plato said: "Wisdom is worthless without experience and alacrity."
It is related in Roman literature that the emperor was once riding and passed through a thick forest where he came across a philosopher. He ordered that he be summoned but the philosopher did not reply. The second time the emperor himself summoned him and he still did not reply. When the emperor saw this, he went to the philosopher and asked him what he was doing in that forest. The philosopher replied: "I am learning wisdom". "In that case", said the emperor "teach me some of it". At this, the philosopher took a piece of paper and wrote upon it: "Whatever you may decide to do, first think of the possible outcome". He handed the paper to the emperor who took it and on his return to Rome he ordered that this paper should be placed at the entrance to his palace. At that time some evil men were angry against the emperor and sought to assassinate him: they promised gold and jewels to his barber. The barber agreed to cooperate if they could assure him that his life would be safe. They promised accordingly. Then came the day when the barber went to shave the emperor, according to the plot. When he came to the entrance of the palace and looked up and noticed the letter given by the philosopher and its contents "Whatever you may decide to do, first think of the possible outcome". He grasped the meaning of this words and was deeply shocked since he thought that the emperor had instructed that the letter should be placed there after he had learned about their plot. He immediately went and fell on his knees, at the king's feet and he cried and beseeched his forgiveness. He then told everything about the conspiracy they had schemed against him and about which the emperor had no notion. When he heard this, he had the plotters brought before him and put them to death and released the barber. He then sent for the philosopher who had given him the letter and he retained him at his side all his days in affection and great honour.
Notes of the translators:
 This probably means that the wise man thinks ahead.
 Probably something good happened to him , which he did not foresee.
 The author presumably means the following day.
The whole book Tzemach Tzadik in Hebrew (printed in Rashi characters) can be downloaded in PDF format and read online at Hebrewbooks.org. Chapter 18 about alacrity and insight is found at pages 38-40.