The Saying by our blessing guru srila sri Durgai Siddhar is doing miracles in everybody's life.
Lives which are born on mother earth should survive according to their karma and purva punya. The lead to understand what is our karma and purva punya should be guided by a person named GURU (means "Shows the right path"). It is very hard to find a right person as guru and even its not in our hand to choose the right person which am going to get, will take me to the end of the world by all means of my karma and my soul, .
When you get a final option to choose a person, Go for it. Don't think or take any decision in dilemma because it is your last chance. Some people according to their philosophy and dharma, they say you can change your guru with his permission (it may be right)but for my aspect it is something like, giving the baby a chance to choose its mother for recognizing the world of knowledge. How can you switch your mother instead of the previous one. Don't even think about it.
A new born baby will cry at the very next moment it came out because of change of climate and place. the same way a shishya who is like a new born to the guru will have so many doubts and queries will cry like a baby to solve them. being a matured mother a guru will take initial step to make the kid understand the problem and solve what is actually important at the moment. The methodology of solving the issue is called Upasana. The one who solves using the ways which his guru taught was Upasaka.
However the upasana and the upasaka can vary in so many terms but just to explain it in a simple way. The Sishya will be called as upasaka, the subject which taught by his guru will be upasana.
The day when a human born, he will be accompanied by three things namely, karma,gnana,yoga. which will not come in his life until he search them are Gnana and Yoga. but as far as Karma is concerned it will stick on to you it won't leave even if you leave this mother earth. So to leave the karma, one should lead a spiritual life and live according to dharma and should do your duty assigned to you. To know what is your duty you need a person to tell you, he is none other than your Guru.