The informant first heard this proverb when she found out that her crush had just gotten a steady girlfriend in the seventh grade. Her best friend realized how sad she was because she had been silently moody all day long. When she found out the reason why she tried to explain to the informant that “there are plenty of other fish in the sea,” meaning that there are many different types of guys in the world. If you don’t catch one, there is always another one that you might want more, and maybe if you didn’t catch this one this time, next time it will be even better when you do manage to catch it. The informant believes that this saying is just for immediate comfort, for the best thing that any good friend can do is listen and think of ways to help their friend feel better about themselves. She retells the proverb because she has been through that experience before and it always feels better to help someone through something that you overcame in the past.
It is true that there are always plenty of other fish in the sea. However, this saying doesn’t always work, since emotions are hard to control. The saying very much reflects the optimism of our society though. The United States is a very future-oriented society, where we are always looking toward the future, saying “forget the past, think of all the possibilities for the future!” I think people say this to their depressed friends because it helps motivate them to look toward the brighter and better future, where they are in control of what happens in their lives and they are the only ones who can choose when and where they will be sad or happy and they won’t let any single guy prove them wrong.
There is in interesting cartoon by J. Hitchcock and Zahn related to this proverb at http://www.cartoonstock.com/directory/p/plenty_more_fish_in_the_sea.asp .