Advancement of the Gospel

Some of the most difficult circumstances Paul faced in life he met them with joy and looked at them as an opportunity for the advancement of the Gospel. How could imprisonment, beatings, hunger, peril, danger etc be used for the Gospel? Paul say's in his letter to the Philippians that what has happened to him was for the "advancement of the Gospel" How so? Furthermore how can we use our circumstances for the advancement of the Gospel? Could we say that God permits us to be in the circumstances so that the Gospel would be advanced? How do we know?