The suffering of change is one of the three kinds of suffering described in Buddhist tradition. Recall that suffering, as opposed to pain, is an uniquely human experience. Animals can feel pain, but they do not suffer because they do not have concepts or ideas about how the world "should be." Animals do not decide that an event that is happening or has happened is unfair or unjust; they live in the now and accept what is.
Humans, on the other hand, do all the above. We fight what is; we insist that the real world be congruent with our idealized view of it. One of the concepts that causes endless suffering is the belief that good things should stay the same and resist change. Whenever we find a moment in our lives that is sublimely pleasant, we want to hold onto it, we never want it to go away, we want to make this perfect moment permanent. Suffering comes when we realize that all experiences and all things in the physical world are transitory. When we try to hold on to youth, we encounter the impossibility of that effort. When we wish for love to remain unchanging, we are sorely disappointed. Whenever we try to create certainty in this uncertain world, we encounter the suffering of change.
Facing the suffering of change is to know that this moment is ephemeral...to resist the idea and the desire to keep it. By knowing that the moment is real only for right now, we are less likely to demand that it stay and remain exactly the same. We are capable of re-training our minds to appreciate and be fully present in the now. The more we practice this, the less we will suffer. It is an effort, but the results are well worth it.