The Indian spirituality believes in four principles.
First: That whatever happens, had to happen that way. You could not change it.

Second: Whoever you meet in your life, you’re supposed to meet and there’s a purpose in meeting that person. There’s no chance meeting with anybody. It’s all based upon your past actions and they have come either to teach you something, learn something, pay off something, receive something and it’s only to settle something that you meet anybody in life.
The Third is: whatever has to start in this life… where you say, “I want to plan this. I want to do this.” There’s a time fixed for this and it can only happen at that time, neither before nor later.
And the Fourth Principle is the most important one. It says, what is over is over. Don’t hold onto it. Don’t hold onto the past… don’t hold on “Oh, I made a mistake. I should not have done it.” There was no way. Hindsight can do a lot of things which the real information at the time would not have done. You would have done exactly the same thing.
Then why regret? Why carry guilt with you? Carrying guilt lowers your energy, lowers your power to concentrate. It’s an interference in your meditation. So we must learn how to overcome this feeling of guilt.

Summary –

• Whatever is to happen, will happen that way.
• Whoever you have to meet, you are meeting for a certain reason and not by accident or chance.
• Whatever has to begin at a certain time, it will begin only at that time, neither before nor after.
• What is over, is over.

source – http://IshwarPuri.org/