So there's this old guy in a boat, and the boat is in the ocean, right? Except the old guy actually represents his own consciousness, and his boat kind of represents his mental framework for understanding the world, I guess. Without the boat, the old guy would die and merge with the ocean. And the ocean represents his unconscious, obviously. 

When the old guy (consciousness, remember?) fishes in the ocean (unconscious, by the way), that's like having an idea, or recalling a memory or something. So, the old guy isn't really in charge of what specific fish (idea, as I said) he gets, that's all up to the ocean (unconscious, if you remember). He can take his boat (that's the mental framework, or, you know, whatever) to specific waters to have a better chance of getting the fish he wants, but it's all about patience and having faith, sort of. 

If the old guy catches a fish he doesn't want, he can just toss it back in the ocean. If he loves it, he can put it in a fish tank and put it on display or something. If it looks delicious, he can eat it. He can basically do whatever he wants with the fish, and he won't run out any time soon because of how damn big the damn ocean is.

Anyway, don't go mistaking yourself for a fish, or a boat for that matter. You're an old guy. Well, technically you're the ocean pretending to be an old guy so that the ocean can experience itself, or something like that. All things must return to the ocean eventually.