People know so many possibilities to hurt them self and others. This capabilities are as many as them self. Unfortunately on Dreamstime I found less those examples then the ones that illustrating people happiness. That is optimistic.
One of most obvious form of suffering is physical pain, when our body is telling us that something is wrong. We show hurt with unhappy, sad faces, objects that could hurt us, body with some color hurting parts.
We suffering also with some psychical way, when we hurt us self with some bad thoughts or someone else is hurting us with words.
It also happened some accidents, some of them are happening because our inattention other by someone else.
Hurt sense is showing us how wonderful and precious are those days when everything is all right and enhance our happiness.