happy/sad brain chemistry, mania

  1. If someone is happy, will they always become sad after a while? Is it just due to the difficulty in getting their all their needs met, or do they run out of the brain chemicals related to happiness or something?

  2. If allowed to roam free, does a manic person who feels happy always stop being manic after a while?

1)a) If someone is happy, will they always become sad or frustrated (or another negative emotion) after a while?