A more detailed elaboration from the earlier post of Goenka's quotation.
"We constantly blame external things, people or situations for our sufferings. ‘It’s because of that person I am unhappy’, ‘that person did or said something that displeased me, that’s why I am miserable’, ‘if this situation in my life changed, then I could be happy’. We believe 100% of our happiness or pain is caused by things out there and that if the world was just as we wanted it to be then we would be at peace; if we had everything and everyone we wanted then life would be perfect. What we fail to realize is that the external world comes and goes, people and places come and go, things just happen, they are neither good nor bad, right nor wrong, they just are. It is only in our reaction to them, and our labeling of them as things that either give us pleasure or pain that misery arises. 100% of our suffering is caused inside, by our reactions to the things we perceive as happening outside of ourselves.
For example, someone in your life acts in a way that displeases you in some way, they do not conform to what you would like them to do or be. That particular situation in itself contains no suffering, it has no intrinsic pain in it, a person has simply chosen to act a certain way, they are not forcing you to be unhappy. It only becomes a source of suffering when you perceive it as producing pain in you and you react, demanding that the person change what they are doing or be different in order to please you, to give you pleasure rather than pain.
Things happen and you choose to react and let them trouble you, no one else but yourself is causing the misery. It is always your decision to react. Buddha therefore discovered that in fact 100% of all suffering is produced by our reactions to sensations in the body apparently being caused by people and situations outside of ourselves, 0% is in fact caused by the people or events themselves.
With these realizations, Gotama set about developing a solution to this universal malady, and began investigating and dissecting sensations and this root level of the mind. The solution he found was a technique of meditation he referred to as ‘Vipassana’. "