According to Iqbal, this collective ego of humanity is real. Individual ego is virtual. Hence individuals need to extinguish their egos, or selves, in the collective ego in order to become real.
A nation which adopts the Unity of God as its basic principle becomes the collective ego on earth.
Islam is one such nation, and hence for a Muslim the way to realize his or her self is by extinguishing their individual self in the collective ego of the nation. This has been explained in ‘Asrar-i-Khudi’ (1915) also but in more detail in ‘Rumooz-i-Bekhudi’ (1918) (both parts together form Asrar-o-Rumooz, the first published book of Iqbal’s poetry).