Some of us know that darkness is nothing but lack of light... similarly foolishness is nothing but lack of wisdom & many such instances where lack of a positive component leads to creation/presence of a negative component. Yet there are some instances wherein this lack of a positivity is self created. For instance, the biggest source of hindrance to our happiness: Worry. Its a very self created factor that slowly and steadily creates lack of happiness and a positive attitude.
Ever wondered what causes this worry? Well, you conviniently welcome negative thoughts about something in your mind and create a cozy place for them to grow. Once they are at home, they begin to multiply and start linking themselves with the most illogical reasonings. The result: You begin to feel burdened, heavy (heart) and sad. And then we blame the world for not being such a nice place to live in.
What I've said above may sound like a theoretical explanation of some bacterial infection, but then think of it. Isn't it worse than one? Atleast you can cure yourself of bacterial infection through medicines, but what about a self acquired, self propogated and self raised infection? This can't be cured unless you gear up to eliminate negativity from your mind, body & soul.
Worrying has never helped any cause, nor has it solved any problem. Then why not just keep happy and let things happen through efforts? Just imbibe all the positivity you can and throw off any negative thoughts that try to creep... the result would be a body, mind and soul thats full of energy, happiness and purity.