Eternal life. Sounds good doesn't it? No old age, illness, or death by any means? As one who has lived such a life, there is a former Jedi Master who can tell you that it is a curse. She once had friends, and a family. One by one, they were taken from her, either falling in battle, or dying of old age.
Why did this happen to a Jedi? She made a choice that the force did not approve of. She used an ancient Sith weapon on the planet Malachor to cut off all Sith from the force. She decided to do this to end a long war, and believed that it was her only choice. With the Sith defeated, the Republic, and the Jedi Order, rebuilt and prospered. It would be centuries before the Sith became a threat again.
The force chose to punish this Jedi for her actions, causing her to reverse in age several years, to the age of twenty five, and then deciding that she would not age a single day ever again, until the force were brought into balance. That day was almost four thousand years ago.
At first, she continued to live her normal life as a Jedi Master, soon becoming Grandmaster of the order. She would hold that position for over eighty years, until the day her daughter died of old age. By that time, she had already lost everyone else dear to her, including her husband, who gave his life in a noble sacrifice to save thousands of lives.
On the day of her daughter's death, the Jedi attempted to take her own life for the first time, failing miserably, as her self inflicted wounds healed within seconds. That was the most painful day of her life, and when she thinks about it, she still breaks down into a sobbing mess, just as she did when it happened.
After some time in mourning, she resigned from the Jedi Order, and left her identity behind, only taking her ship and trusted astromech with her, as she set out to make a new life for herself. The first of hundreds of new identities she would assume, all being false names to her, with no meaning. The only name which she felt had meaning for her was...The Cursed One.
Since the day she resigned from the order, she has not identified as a Jedi, and now walks a path of balance, using all aspects of the force, but letting neither the light, nor the dark control her. She has stayed out of the galaxy's wars, feeling that they only feed the continued imbalance.
The Cursed One has occasionally discovered force sensitives, and has trained a few to walk the path of balance like she does, but most end up drifting to one extreme or the other, such as the most powerful student that she trained.
The strange boy was discovered on the outer rim planet of Zerron, about three thousand years after the former Jedi should have died of old age. When she first saw him, she did not believe him to be sentient, and thought he was a creature of the swamp. However, she realized her mistake, as she saw him use the force to steal food from street vendors, and jump across rooftops.
She followed the boy, and eventually cornered him in an alley. She said to the frightened child "I will not harm you. I can help you."
"Help me, how will you?" The boy asked.
Interesting dialect. It's going to be fun talking to this one! The Cursed One thought to herself, before saying "You have a power that you do not yet understand. I can teach you to understand it, and perhaps use it for something greater than childish games!"
"Oh, Jedi are you?" he asked.
She laughed, then said "I used to be."
The boy hesitated, before saying "Learn from you, I will."
She nodded, then asked "What is your name, child?"
The boy said "Yoda, my name is."
"Yoda, I am pleased to meet you. You are very strong in the force, and I look forward to teaching you. As for my name, you may simply call me master." The Cursed One said.
"Master, a good learner, I will try to be." Yoda said.
"Lesson one. Do, or do not. There is no try!" The Cursed One said.
The Cursed One trained Yoda for several years, until the day he decided to join the Jedi Order. She was not pleased, as she had foreseen a terrible future for her apprentice. She chose not to tell him the full extent of what she saw, only giving him a warning that if the Jedi became complacent, then they would one day face their end.
Over his long lifespan, Yoda drifted further and further from The Cursed One's lessons, eventually becoming a very traditional Jedi, who rarely contacted her. She had become close to him during their time together, almost treating him like a son, and their growing apart over the centuries was painful for her. Nevertheless, she accepted that Yoda had the right to live his life however he saw fit, even though she did not agree with his views on the force.