All beginnings are from Purim.
Meaning, that the starting point for people today is from Simcha, as opposed to previous generations where things began from Mussar and ethical rebuke in order to wake up and do teshuva.
However, since today people are so morally weak that even a little bit of mussar can knock them down, the attitude must be one based on simcha and a positive outlook on oneself.
The simcha of Purim is so important that it is the opening for the joy during the entire year.
Reb Noson wrote a prayer to be used as a springboard to enhance the Purim experience and joy:
And it is specifically through the acting silly and foolish on Purim that a person taps into the joy of Purim.