Did you know that both sharks and goldfish will get as big as their environment allows? So if you had a small shark and kept it in a small tank, it would remain small but if you let it out into the ocean, it would get big enough to eat a human being.
Sharks (and goldfish) are just like your negative thoughts. When you feed them and give them room to grow, they will get big enough to sabotage your every dream. Yet when you contain them and instead nourish your positive thoughts, your negative thoughts will remain small and in fact shrink as your positive thoughts take over.
What you fuel grows, what you starve shrinks. Look closely at the thoughts you nourish, are they negative or positive? It can be challenging to break old habits, and necessary when you want to create a new and better life each day.