Guru is the one only thread that enables us to reach the final goal
According to Vrihadaranyak Upanishad, our existence consists of 3 bodies, besides
SOUL, the notion of three bodily levels is described as :
Physical body (Sthool sharira)- The sthula-sharira is the gross external form, corresponding roughly to the physical body known to materialist science. This sharira is shed at the point of physical death, although the personality continues to exist, operating through the sukshma-sharira.
Astral body (Sukshum sharira)-The sukshma sharira comprises an `inner` (Antahkaran) and an `outer` (Bahyakaran) instrument. Bahyakaran is the collective term for the five `sense capacities` (buddhindriya) plus five `action capacities` (karmendriya). This `subtle body` is capable of migrating from one Sthula-sharira to another, thus engendering the process of reincarnation, the world can only be experienced when both sthula- and sukshma-sharira are present.
Cosmic body (Kaaran sharira)-The Karana-sharira or `causal body` is so-called because of its status as `the original embryo or source of the body`." It is not even remotely `body-like`, but may, rather, be equated with prakriti as the unmanifest potential for embodiment. It can also be called as mahat or buddhi, the initial evolutes of this unmanifest potentiality.
The verbal root of sharira is sri meaning "to fall apart", while `support or supporter`, is another possible source. Both roots have “secondary” connotations. Each sharira consists of a covering or a form. In other words, its an upadhi that masks the true nature of the Self (atman), and must therefore be successively discarded (if you mean we need to attempt to do away with the upadhi / masks) with.
When one religiously follows spiritual practices and is blessed by a realized soul, his Cosmic body gets merged with Super Consciousness, which is called Salvation or “Moksha” state. He remains in a blissful state of mind and all the cells of his Physical body become divine. As his consciousness becomes universal, he is regarded as GOD in human body.
The scriptures define him as GURU SAAKSHAT- PARAM BRAHAM, where Saakshat stands for being physically present. In words of Kabir "Kabira te nar andh hain, guru ko kehte aur. Hari ruthe guru thor hai, guru ruthe nahin thor"- Meaning those are blind who differentiate between God and Guru if due to your Karma (deeds) God is angry Guru can protect but if your Guru is angry, even God can’t help you. Hence a complete surrender to the Guru is a must.
To get a Guru who takes you as his own is really one-in-a-million chance. He has to have a level of Compassion of God himself to help you tread the path of your salvation - Moksha.