There was once a king named Vaikhanas, who was ruling Champaknagar. He had envisioned in his dream that his father had fallen to hell. He related his dream to vedic brahmanas and asked them how he could deliver his father from hell. Brahmanas suggested that he should approach Parvat Muni. Seeing his grief Parvat muni said, "Since your father was very lustful in his previous life, he had got such a plight. All of you observe the Ekadasi that comes on the bright fortnight in the month of Agrahayan and offer the fruits to your father." He returned to his palace and observed the Ekadasi. Due to this pious activity his father got liberated from the hell.
The main duty on the day of Ekadasi is to completely satisfy Hari and His devotees with all the senses. The true meaning of "upavas" is to stay close. On the day of Ekadasi, one should reside close to the Lord with transcendental qualities, being freed from all sinful activities, giving up all familial and material activities and rejecting all material sense pleasures. But it is impossible to stay near Him with material body, mind and intelligence. So how is it possible for the enslaved jivas to stay close to the Lord? It is impossible to worship Sri Hari without accepting the shelter to the lotus feet of a bona fide guru, who is srotriya (expert in Vedic knowledge), brahma-nista (Firm faith in the Lord) and dearmost of Sri Hari.
Unless one is favored by a pure devotee, one cannot attain the platform of devotional service. Till the point one is away from Krishna-bhakti, one cannot even be relieved from the bondage of material existence.
The spiritual master is non-different from Krishna. Evidence can be seen in the revealed scriptures. Lord Krishna in the form of the spiritual master delivers His devotees.