The agony of knowledge
The agony of realizing that your loved one will leave you as soon as they meet someone better able to provide for their needs.
The agony of learning that one holds a belief because of being weak enough to need a belief, and not because the belief is true.
The agony of hearing your children condemn all you ever believed in and tried to teach them.
The agony of learning that you have lost your ability to actually see, enjoy, and learn from Nature, and that for all your life's work and experience, children possess greater wealth.