We sometimes fail to realise that when we pray to Allah we are in fact performing a great act of ibadah (worship). On the surface it might seem as if we are asking out of self-interest, but we are really proving the sincerity of our belief in the tauhid (Oneness) of Allah and our submission to the True God. Thus the Prophet pbuh said: "Supplication is itself the worship." (Reported by Abu Daud and al-Tirmizi, sahih.) If a servant prays the whole night to Allah, he therefore performs a great ibadah all night long.
Mohd Asri Zainul Abidin, Islam in Malaysia: Perceptions & Facts
islam, spirituality, submission