Pesach is G-d's initiative, corresponding to the pre-natal epoch of knowing all knowledge.
The first day of the omer is the post partum, the forgetting of the angel, where our initiative kicks in.
Shavuot is again G-d's initiative, the 50th day is not counted, no longer our initiative.
The counting is a building process. That is why each day's count includes all the previous days. Using the 48 ways, the first 32 days are about issues between person and person; the last 17 are about issues between person and G-d.
The omer is a barley offering; food for animals, showing our elevation of the physical to the spiritual.
Pirke Avot 6:6 states that "the crown of Torah is acquired by 48 Ways." Each of these 48 Ways is a special tool to help sharpen our personal skills and get the most out of life. The 49th way (day) is a review of all the previous days.
The lesson of the Counting of the Omer is clear: Each day counts; each Israelite counts; each mitzvah counts.
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OMER mentioned Va-Yikra / Leviticus 23: 15-16 Devarim / Deuteronomy 16: 9 -10
This is a period of national semi-mourning (no weddings or even haircuts). It was during this period that Rabbi Akiva's 24,000 students died for not showing proper respect towards each other. It is a time for reflection upon how we look upon and treat our fellow Jews and upon the tragedies that have befallen us because of unfounded (self-justified) hatred.
Note that the 33rd word in Torah is TOV, GOOD, indicating that Lag BaOmer is a good day for us. The Gematria of "TOV" is 17; 17 days left after l'ag b'omer. The gematria of lev tov = 32+17 = 49, the levels of progress from the Omer offering.
The Zohar reports that in Egypt the Jews had slipped to the 49th level of spiritual impurity. (50 is the very lowest.) Hashem could not give the Torah at this point. The Jews needed to grow up first, or else they would have squandered the opportunity.
An omer is about 3.3 dry quarts.
Passover is the feast where we celebrate our physical freedom, Shavuot the feast where we celebrate the ultimate holy development of a free Person, ready to receive the Torah.
Shavuot takes preparation, like the other holidays -
Stay up all night studying to atone for the generation in the desert who fell asleep the morning of Matan Torah.