Countdown and Countup
Lag B'Omer marks the two-thirds point in the long, seven-week counting of days between the festivals of Pesach and Shavuot.
Our commentaries point out that the counting of days mandated by the Torah between the festival of freedom and that of receiving the Torah expresses the profound longing of the Jew to reconnect himself to Torah. While such longing in material matters finds expression in a "countdown" of days left to go before reaching a goal, the sefirat ha'omer counting between Pesach and Shavuot is one of a "countup" of how many days have passed.
One reason for this is that a Jew must feel that he must grow each day from the stage of physical freedom which Pesach celebrates to the stage of spiritual freedom which the festival of the "Giving of the Torah" celebrates.
In the same manner it is crucial for Israel to grow from its material success in creating a Jewish state to the level of a spiritual success, the sort of "countup" which will secure Israel forever.