How do you feel after Shavuot? On the sixth of Sivan we reached the heights of receiving the Torah; we studied all night; we read the Book of Ruth about the roots of the Kingdom of the House of David – and now, after the holiday, we have to get back to routine, work, news and politics.
How is it possible?
Our sages had compassion on us and delayed resumption of saying Tachanun [the prayer of supplication] until the 12th of Sivan, since "tashlumin kol shiva", one can redress the failure to bring the offering for all seven days (Chagiga 17:1) – while the Temple existed, the holiday sacrifices could be completed during these seven days (in practice, it was customary for only six days).
These days are the continuation of receiving the Torah, days of joy, and therefore, we do not put our heads down and say Tachanun while praying as on ordinary weekdays.
In the book Hemdat Yamim it is written that these days: "during these days, one must always keep their eyes focused on Mount Sinai, and imagine how the Jewish people stood in purity facing the mountain before God".
It is difficult for a Jew to leave Mount Sinai, so we try a little longer to stay at the bottom of the mountain. These are days when it is possible to complete the receiving of the Torah, so whoever feels that they missed out – there is time to make it up until the 12th of Sivan.