Service is life. No service means, spiritually no life.
The essence of Hinduism is the same essence of all true religions: Bhakti or pure love for God and genuine compassion for all beings.
Pure devotional service fries the seeds of material inclinations in our heart.
Giving up pride means giving all credit and glory to Guru and Krishna.
Theoretical knowledge can not touch heart without Humility
The essence of spiritual life is simply to use our free will properly.