Guru is one who knows God, and who shows the way to Him. To follow a divine manifestation is the sure way to God-realization. One who knows God becomes the speaking voice of the silent God.
— Shri Paramhansa Yogananda
God manifests through the Guru.
We are all an image of God - but we haven't yet realised our true self. It's a Guru who has found/realised God within and reflects his true nature. For Guru, there is no separation from God, he has become one with God, he has become the ocean.
A Guru is an image of God. He/She may have gone through all phases of life as we are but on the journey, a true Guru has discarded the ego personality, and is governed by the Soul, the true image of God.
A guru is a God-knowing person who has been divinely appointed by Him to take the seeker as a disciple and lead him from the darkness of ignorance to the light of wisdom.
— Shri Paramhansa Yogananda
The Guru is selfless, he is not thinking about himself/herself rather thinking of his disciples and how to take them forward and help them achieve their ultimate destination - self-realisation - and then to liberation.
A Guru carries a big responsibility, not just for a few years, decades but for many lifetimes. It's the eternal connection with his/her disciples and responsibility of guiding them in achieving their ultimate goals. Guru's goal is to help you, see you through all your ups and downs and help you achieve the same liberation, peace, bliss, God realisation that the Guru has achieved.
The disciples are very fortunate to find an eternal bond with their Gurus. This relationship is not just based on discipline, following the teachings (although, that is important), it is a form of eternal friendship that has continued from many lives.
In return, the Guru doesn't ask for anything. Disciples, however, offer their love, and the most loving offering to the Guru - is following the teachings and practising the techniques. If the disciples want to offer further, they can help Guru spread their teachings, messages.
A guru's only interest is to help you progress spiritually. If the teacher wants something from the disciple, he is not a master. The master's only desire is to give, not to take. But if the disciple has the wish to help the work of the master, that is to his credit — he is helped by giving to God's cause.
— Shri Paramhansa Yogananda
The Guru-Disciple relationship is eternal.
Even when I am gone my help will always be given to devotees all over the world, if they keep in tune. Never think for a moment that when I am physically absent from you all I am not otherwise with you. I shall be just as deeply concerned for your spiritual welfare when I am no longer in this body as I am now. I shall always be watching over each one of you: and whenever a true devotee thinks of me in the silent depths of his soul, he will know that I am near.
— Shri Paramhansa Yogananda
Happy Guru Poornima
Aum Prem
Akhil