Buddhists believe suffering comes from clinging to things which are impermanent. Of course it isn't that simple. At the very least there have to be many kinds of suffering many of which simply ARE. I doubt people dying from disease are clinging to the source of their suffering. Old age comes as a natural consequence and can't be said to be a result of clinging to something unless you stretch the example and say these folks are clinging to their lives. So the simple version is that SOME kinds of suffering result from clinging to things which we shouldn't. But other kinds of suffering have to be overcome to create other gains. Take cycling for example. Climbing those hills around Cheaha will absolutely cause you to suffer! By enduring the suffering, one gains strength and either will endure less suffering to perform the same task (or possible be able to suffer at an even greater level). It becomes a necessity for a person to understand which kind of suffering is necessary or ...
“Life’s under no obligation to give us what we expect. We take what we get and are thankful it’s no worse than it is.” ~ Margaret Mitchell