We suffer without choice. We do not want to suffer and we try everything to be happy but suffering happens regardless of our wishes, and we can't do anything about it. Why is this so? It is because we have already created the causes for suffering in the past.
But where are those causes of suffering? They are within your mind right now, it is the self-centered mind and all the disturbing emotions that come from it. If you recognize this, you will understand that you are responsible for your suffering and that there is no one else to blame. Understanding this you will be able to tolerate difficulties and avoid more suffering in the future. If you want to be happy you must know the causes for happiness.
Those who wish to crush the many sorrows of existence,
Who wish to quell the pain of living beings,
Who wish to have experience of a myriad joys
Should never turn away from bodhicitta.
Should bodhicitta come to birth
In those who suffer, chained in prisons of samsara,
In that instant they are called the children of the Blissful One,
Revered by all the world, by gods and humankind.
For like the supreme substance of the alchemists,
It takes our impure flesh and makes of it
The body of a Buddha, jewel beyond all price.
Such is bodhicitta. Let us grasp it firmly!