The Buddha was asked "what is the cause of suffering?"
His answer was very direct and simple.
The Buddha said that suffering has three causes:
1) There is something you want, that you cannot have, it causes you to suffer
2) There is something you have, that you are frightened to lose, it causes you to suffer.
3) There is something that has happened that you did not want, it causes you to suffer.
The Buddha was asked, what is the solution to our suffering?
He answered, by staying present and not wandering in your thoughts of past and future you will remain calm and serene. It is the entrance to peace and healing.