Gautam Buddha said that the single factor responsible for bringing us to earth repeatedly is “attachment;” if and when attachment is transcended one achieves liberation. Yogis over millenniums of research designed methods to do this; bhakti-yoga or path of devotion for those whose heart or sentiments are strong e.g Meerabai, Surdas or Jesus; jnana-yoga or path of knowledge for those whose brain or thinking is strong e.g. Buddha, Janak, Raman Maharishi or Socrates; and karma-yoga for those who act or serve without caring for result e.g. Mahatma Gandhi or Mother Teresa.
It was no ordinary happening when saints blossomed like mushrooms around sixth century B.C; Buddha and Mahavir in India, Pythagoras in Greece, Zoroaster in Unan (now Iran), Milarepa in Tibet, Druids in Europe and a few notable saints in China. According to Madame H.P.Blavatsky, founder of Theosophical Society, earth developments had reached three-and-a-half rounds out of seven in which the clock needle would complete its full circle.
It was the time to turn back to your origin after completing all experiences and learning, a goal towards existence as “perfect beings” in cosmos finally. These gurus were divinely destined to provide spiritual guidance to humans round the globe according to their making. After these big-ones a chain of gurus followed in every religion to turn human’s attention towards their real purpose of life.
Many more methods came into being: Tantra, Mantra, Hatha-Yoga and so on. However, all these methods are based on self-efforts and take a long time to produce results. If one can find a jnani (wise man) and surrender to him/her with faith, quick results are possible because of Shaktipat (passage of energy from guru to disciple) and what would be achieved otherwise in 40 years could be achieved in 40 days, hours or even minutes. Shaktipat gurus are normally hidden from public eyes as pointed by Guru Gobind Singh.
One should realise that this physical world and relations are only to learn lessons, not for possession; inner peace, liberation and permanent home up there can be found only by seeking spiritually.