Torah, Devarim, 16:09 – 16:10: You shall count seven weeks for yourself; from [the time] the sickle is first put to the standing crop, you shall begin to count seven weeks. And you shall perform the Festival of Weeks…
After Passover, we start preparing for the summer and harvest time. This is the time when one cannot make big corrections.
In the corporeal world, this is symbolized by the prohibition of haircuts and other behavioral laws. These laws say that at this time, a person cannot engage in serious corrections because there is not enough Light and strength for it.
This period is called the time of the small state, Katnut, and therefore, there are no holidays during this period. It is forbidden to celebrate weddings, buy new things, and so on. This means that we are not armed with greater forces against our own egoism because all this time, we are preparing ourselves to receive the upper Light on Shavuot.
Within 49 days, there is a gradual accumulation of the right desire, which is corrected in very tense states, and then it breaks through, reveals itself, and the upper Light, which is called “Giving the Torah,” reveals itself within it.
From KabTV’s “Secrets of the Eternal Book” 8/10/16