The transformation that occurred at Yetzias Mitzrayim, from a slave mentality to the spirituality of “naaseh venishma” was miraculous. How did it occur? With the mitzvah of Sefira, taking it "one day at a time".
Why then, was there so great a failure at the episode of the golden calf? Perhaps because it was only 49 days, not 90.
Bnei Yissaschar notes that the giving of the Torah was a “wedding”, a union of Hashem and Klal Yisrael. Prior thereto, the Jews had been bound to the avoda zara of Egypt. He then asks, the halacha says that a widow or divorcee must wait 90 days before taking a new husband. Shouldn't there have been a 90 day waiting period before Mattan Torah?
He answers that beginning with the 7th day of Sefira, we do a ‘double count,:” e.g., “today is seven days, which is one week. Today is 11 days, which is one week plus four days. Thus we count six single days, and 43 “double days.” The double days = 43 x 2 = 86, plus 6 single days, so you have more than the requisite 90.
(Rabbi Twerski then adds in jest:) But if so, why did they relapse to the avoda zara of the golden calf?
Because the program requires 90 meetings in 90 days. Doubling up and making 90 meetings in 45 days doesn’t work.