Pain is an Occurrence. Suffering is an Interpretation.
Immense pain may not lead to suffering for some. Immense luxury may be, however, enveloped in utmost suffering for many.
Suffer comes from Latin – sub up + ferre to bear. Bearing is not acceptance but tolerance of reality. You bear the burden. Forced to carry what you consider is not yours to carry. If it was your own, then it wouldn’t be a burden. What is unpleasantly deviant from what is considered as “Self”, is a burden.
There is always an expectation from the Nature and the “God”. The expectations are categorized. A long as what we consider as good is encountered, there is no suffering. As soon as our experience matches expectation under the “Bad” category – we suffer almost automatically.
The mapping of what we perceive and encounter and how we act or feel is baked into us as our instincts. This baggage of the past – comprising of entire human-kind, perhaps existential history, is used to create newer or reinforce earlier mappings.
Suffering and Joy keep alternating because we keep comparing every moment – unique as it is to a predetermined standard and a past map. A map that is of mind… and of the past. Insufficient and incapable of predicting the present moment.
If we were content to live as “witnesses” of all the moments we experience, without judging or categorizing (such that we are not in constant reaction) we would be free from the results of our Karmas. The pain may still be encountered, but it will not lead to Suffering! Being aware of the maps, but not letting them dictate our actions is freedom.